Scalloped Portobello Mushrooms with Creamy Garlic Cheese Sauce
Craving a rich and savory side dish for dinner? Our scalloped portobello mushrooms feature thick slices baked until tender in a creamy garlic sauce topped with bubbling cheese. The key is in the broth reduction, which concentrates flavor while helping the vegetables hold their hearty texture. It’s a comforting, low-carb bake that pairs beautifully with roasted meats or stands deliciously on its own.
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Ingredients for Scalloped Portobello Mushrooms
For the mushrooms
- Portobello Mushroom Caps – Large and meaty, these are the star of the dish. Be sure to scrape out the gills for the best texture.
- Olive Oil – A good drizzle helps the mushrooms roast up perfectly.
- Kosher Salt – Enhances all the flavors without being too harsh.
- Black Pepper – Freshly cracked is always best for that little kick.
For the creamy sauce
- Unsalted Butter – The base of our rich, velvety sauce.
- Yellow Onion – Thinly sliced and caramelized for sweet depth.
- Garlic – Minced fresh, because powdered just won’t do here.
- All-Purpose Flour – Helps thicken the sauce to luscious perfection.
- Whole Milk – Adds creaminess without being too heavy.
- Heavy Cream – For that indulgent, silky texture we all love.
- Fresh Thyme Leaves – Stripped from the stems for earthy freshness.
- Ground Nutmeg – Just a pinch adds warmth and complexity.
- Gruyère Cheese – Shred it yourself for the best melt—trust me.
- Parmesan Cheese – The salty, nutty finish that ties it all together.
Cook Time for scalloped portobello mushrooms recipe
I know we’re all busy, so I always appreciate knowing how much time I need to set aside. This savory mushroom casserole with Gruyère does take a little time to build those deep, creamy flavors, but every minute is worth it.
Here’s the breakdown:
| Step | Time |
|---|---|
| Prep Time | 20 minutes |
| Cook Time | 50 minutes |
| Total Time | 70 minutes |
The roasting step for the mushrooms is what gives our scalloped portobello mushrooms that perfect meaty texture. For more quick and easy vegetable side ideas that pair wonderfully, check out our guide to simple vegetable side dishes.
How to Make baked portobello mushroom side
Step 1: Prep and Roast
Preheat the oven to 375°F (190°C). Using a spoon, carefully scrape out the dark gills from the underside of the portobello mushroom caps, then slice the caps into 1/2-inch thick pieces. In a large bowl, toss the mushroom slices with olive oil, salt, and pepper until evenly coated.
Step 2: Roast to Perfection
Arrange the seasoned mushroom slices in a single layer on a rimmed baking sheet. Roast for 15 minutes, or until the mushrooms have released their liquid and are tender. Remove from the oven and set aside. Reduce the oven temperature to 350°F (175°C).
Step 3: Build the Aromatics
While the mushrooms roast, melt the butter in a large skillet or Dutch oven over medium heat. Add the sliced onion and cook for 8–10 minutes, stirring occasionally, until softened and translucent. Stir in the minced garlic and cook for 1 minute until fragrant.
Step 4: Create the Creamy Sauce
Sprinkle the flour over the onions and garlic and cook, stirring constantly, for 1 minute to form a paste. Gradually whisk in the milk and heavy cream until the mixture is smooth. Bring to a gentle simmer, stirring frequently, until the sauce thickens enough to coat the back of a spoon, about 3–5 minutes. Remove from heat and stir in the thyme, nutmeg, 3/4 cup of the Gruyère cheese, and all of the Parmesan cheese until melted and smooth.
Step 5: Combine and Top
Gently fold the roasted mushroom slices into the cream sauce until evenly combined. Transfer the mixture to a 2-quart baking dish and sprinkle the remaining 1/4 cup of Gruyère cheese evenly over the top.
Final Step: Bake and Serve
Bake at 350°F (175°C) for 20–25 minutes, or until the cheese is golden brown and the sauce is bubbly around the edges. Let the dish rest for 5–10 minutes before serving to allow the sauce to set.
Pro Tips & Tasty Tweaks
Over the years, I’ve made this cheesy vegetarian mushroom dish more times than I can count. Along the way, I’ve picked up a few tricks to make it even better, whether you’re serving a crowd or just your family on a Tuesday night.
- Flavor Swap: If you can’t find Gruyère, a sharp white cheddar makes a fantastic substitute. It still gives you that wonderful melt and tangy flavor that cuts through the richness of the cream sauce.
- Diet Tweak: For a lighter version, you can substitute half-and-half for the heavy cream. The sauce will be a tad less decadent but still wonderfully creamy and satisfying.
- Prep/Texture Fix: Don’t skip roasting the mushrooms first! This crucial step answers the common question, How do you cook portobello mushrooms so they are not soggy? Roasting drives off excess moisture, ensuring your final cheesy mushroom bake with Parmesan crust is hearty, not watery.
- Storage/Reheat Tip: Leftovers keep well covered in the fridge for up to 3 days. Reheat gently in the oven or a skillet to keep the texture right. For more make-ahead holiday side dish ideas that reheat beautifully, browse our collection of healthy Thanksgiving sides.
Scalloped Portobello Mushrooms
Ingredients
- 4 large portobello mushroom caps
- 2 tbsp olive oil
- 1/2 tsp kosher salt
- 1/4 tsp black pepper
- 3 tbsp unsalted butter
- 1 medium yellow onion thinly sliced
- 2 cloves garlic minced
- 3 tbsp all-purpose flour
- 1 1/2 cups whole milk
- 1/2 cup heavy cream
- 1 tsp fresh thyme leaves
- 1/4 tsp ground nutmeg
- 1 cup shredded Gruyère cheese divided
- 1/2 cup grated Parmesan cheese
Equipment
- oven
- baking dish
- large skillet or Dutch oven
Method
- Preheat your oven to 375°F (190°C). Use a spoon to scrape out the dark gills from the underside of the portobello mushroom caps, then slice the caps into 1/2-inch thick slices. Toss the mushroom slices with olive oil, salt, and pepper in a large bowl until evenly coated.
- Arrange the seasoned mushroom slices in a single layer on a rimmed baking sheet. Roast for 15 minutes, or until the mushrooms have released their liquid and are tender. Remove from the oven and set aside. Reduce the oven temperature to 350°F (175°C).
- While the mushrooms roast, melt the butter in a large skillet or Dutch oven over medium heat. Add the sliced onion and cook for 8-10 minutes, stirring occasionally, until softened and translucent. Add the minced garlic and cook for 1 minute more until fragrant.
- Sprinkle the flour over the onions and garlic and cook, stirring constantly, for 1 minute to form a paste. Gradually whisk in the milk and heavy cream until the mixture is smooth. Bring to a simmer, stirring frequently, until the sauce thickens enough to coat the back of a spoon, about 3-5 minutes. Remove from heat and stir in the thyme, nutmeg, 3/4 cup of the Gruyère cheese, and all of the Parmesan cheese until melted and smooth.
- Gently fold the roasted mushroom slices into the cream sauce until well combined. Transfer the mixture to a 2-quart baking dish and sprinkle the remaining 1/4 cup of Gruyère cheese evenly over the top.
- Bake at 350°F (175°C) for 20-25 minutes, or until the cheese is golden brown and the sauce is bubbly around the edges. Let the dish rest for 5-10 minutes before serving to allow the sauce to set.
Nutrition
Private Notes
Tried this recipe?
Let us know how it was!Nutrition and Health Benefits
While these scalloped portobello mushrooms certainly taste indulgent, they also offer some wonderful nutritional perks. I always feel good serving this dish because it’s packed with flavor and goodness. Portobellos are a fantastic source of selenium and B vitamins, giving you a nourishing boost.
This creamy scalloped portobello mushrooms bake becomes a more balanced meal when you consider the benefits of the mushrooms themselves. They’re naturally low in calories and carbohydrates, making this a great option if you’re keeping an eye on your intake. For more light and nutritious vegetable inspiration, I love our recipes for perfectly roasted broccoli and cauliflower or these tender honey balsamic carrots.
Choosing cheese wisely also adds protein and calcium. For a deeper look into selecting the best produce, the guide on Choosing Quality Portobello Mushrooms is a fantastic resource. Ultimately, this cheesy vegetarian mushroom dish is a satisfying way to enjoy your vegetables.
A Lighter Version of Creamy Scalloped Portobello Mushrooms
I know that sometimes you want all the comfort of a creamy bake but with a lighter touch. Good news—this recipe is wonderfully adaptable! I’ve made a few simple swaps over the years that keep the soul of the dish intact while cutting back a bit.
For a less rich sauce, you can easily use half-and-half instead of heavy cream. The consistency will still be lovely. You could also use a lighter cheese like part-skim mozzarella in place of some of the Gruyère. The key is to keep the roasted mushroom base, as that’s where the deep, savory mushroom casserole with Gruyère flavor really comes from.
These tweaks make it a fantastic holiday side dish idea that feels special without being overly heavy. For other lighter sides that pack a punch of flavor, you must try our grilled sweet potato wedges or this vibrant roasted cabbage. Sometimes, the simplest changes make the biggest difference.
Thoughtful Tips for Special Diets
I love that cooking brings everyone to the table, and I always want our meals to be as welcoming as possible. If you or a loved one is sugar-conscious or managing dietary needs like diabetic-friendly eating, this recipe can easily be adapted. It’s all about making small, smart swaps that honor both health and flavor.
First, this dish is naturally quite low glycemic thanks to the portobello mushrooms, which is a great start. For even better glycemic control, you can be mindful of portion size—a little of this rich dish goes a long way! If you’re looking to reduce fat further, using a lower-fat milk and a sharp, flavorful cheese means you can use less while still getting that delicious taste.
While there’s no added sugar in the recipe, if you ever want to add a touch of sweetness to balance the savory notes, consider a natural sweetener like a pinch of xylitol. Remember, the best approach is always to tweak recipes to fit your life, making every bite both joyful and mindful.
How to Serve Scalloped Portobello Mushrooms
This dish truly shines as the centerpiece of a comforting meal. I often think of the first time I made this scalloped portobello mushrooms recipe for a family gathering; the aroma of garlic and thyme filled the whole house, and everyone gathered in the kitchen, drawn in by the smell. It’s that kind of dish—it creates a moment.
For a classic pairing, serve this baked portobello mushroom side alongside a simple roasted chicken or a juicy steak. The creamy, earthy flavors complement the richness of the meat perfectly. If you’re keeping it vegetarian, it’s wonderful with a bright, crisp salad to contrast the decadent cheesy mushroom bake with Parmesan crust.
For a full feast, consider serving it with other vegetable favorites like these hearty brussels sprouts or a classic squash casserole. No matter how you plate it, this is a dish meant for sharing and savoring with those you love.
Mistakes to Avoid
I’ve made plenty of mistakes with this scalloped portobello mushrooms recipe over the years, and I want to help you avoid them. First, using soggy mushrooms will water down your creamy sauce. Always take the time to properly clean and dry your portobellos. For guidance, I highly recommend this external guide on How to Clean and Prep Portobello Mushrooms.
Another common error is under-seasoning the sauce. Mushrooms soak up flavor like a sponge, so don’t be shy with the garlic and herbs. Finally, rushing the baking process means you’ll miss out on that perfect golden-brown crust. Patience is key for that cheesy mushroom bake with Parmesan crust. I learned this the hard way at my first holiday dinner!
For more cooking wisdom, explore our guide to perfect vegetable side dishes or these crispy jicama fries. Trust me, taking these simple precautions will make your savory mushroom casserole with Gruyère absolutely perfect every single time.
How to Store Scalloped Portobello Mushrooms
I still remember the first time I made a double batch of this scalloped portobello mushrooms recipe for a potluck. We had so many leftovers, and I was thrilled to discover how beautifully it keeps! To store, let the bake cool completely before transferring it to an airtight container. It will stay fresh in the refrigerator for up to four days.
You can also freeze this baked portobello mushroom side for up to three months. I often portion it into smaller containers for easy weeknight meals. When you’re ready to enjoy, reheat it in the oven until it’s bubbly and hot all the way through. This helps bring back that wonderful creamy texture.
For more make-ahead inspiration, you’ll love our potato squash casserole or these maple pecan roasted sweet potatoes. Having a ready-to-go dish makes busy evenings so much cozier.
Try This Scalloped Portobello Mushrooms Yourself
I truly hope you feel inspired to make this creamy scalloped portobello mushrooms dish for your own table. There’s something so special about pulling a golden, bubbling bake from the oven and sharing it with people you love. I think of my grandmother every time I make it, and now it’s become a tradition in my own home.
This cheesy vegetarian mushroom dish is more than just a recipe—it’s a chance to create your own warm memories. Whether it’s a quiet weeknight or a festive gathering, it always feels like a celebration. So gather your ingredients, preheat your oven, and get ready for something wonderfully delicious.
If you’re looking for more holiday side dish ideas, you must browse our collection of healthy Thanksgiving sides. You might also enjoy these easy zucchini fries or this classic sweet potato casserole. I can’t wait for you to try it!
Frequently Asked Questions
How do you cook portobello mushrooms so they are not soggy?
The key is to thoroughly clean and dry them before cooking. Gently wipe the caps with a damp cloth or paper towel instead of rinsing them under water. This helps your scalloped portobello mushrooms achieve a perfect texture instead of steaming in their own liquid.
What is the dark side of portobello mushrooms?
This usually refers to the dark gills on the underside of the cap. While they are perfectly edible, they can sometimes release a dark pigment that tints your sauce. For a cleaner look in your creamy baked portobello mushroom gratin, you can scrape them out with a spoon.
Is it okay to eat the gills of a portobello mushroom?
Absolutely! The gills are entirely edible and safe to eat. They do have a more intense, earthy flavor than the cap. I often leave them in for extra depth in my sautéed mushroom and onion creamy side, but it’s purely a matter of personal preference.
What’s the best way to cook portobellos?
I truly believe baking them into this scalloped portobello mushrooms dish is one of the best methods! The dry heat of the oven concentrates their flavor and gives them a wonderful meaty texture. For simpler prep, try our method for perfect roasted carrots alongside them.
Cozy Vegetable Sides For Every Occasion
If you loved these creamy mushrooms, you’ll adore these other comforting dishes. They’re perfect for weeknights and special gatherings alike.
Roasted Broccoli and Cauliflower – Crispy, tender, and beautifully caramelized with just the right amount of seasoning.
Honey Balsamic Carrots – Sweet, tangy, and glazed to perfection for a pop of color on your plate.
Crispy Brussels Sprouts – Golden and crunchy on the outside, soft and savory on the inside.
Grilled Sweet Potato Wedges – Smoky, slightly charred, and wonderfully hearty for any barbecue.
Baked Jicama Fries – A light, crispy, and low-carb twist on classic fries that everyone loves.
