In a large Dutch oven or heavy pot, heat 1 tablespoon of olive oil over medium-high heat. Add 1 pound of ground Italian sausage and cook for 5-7 minutes, using a wooden spoon to break it into crumbles, until it is browned and no longer pink.
Add the finely chopped onion and cook for 3-4 minutes until it becomes soft and translucent. Stir in the minced garlic and cook for 1 more minute until it becomes fragrant.
Pour in 4 cups of chicken broth, the entire jar of marinara sauce, the can of undrained diced tomatoes, and 2 teaspoons of Italian seasoning. Bring the soup to a boil, then reduce the heat to a simmer and let it cook for 10 minutes to allow the flavors to combine.
Add 8 ounces of uncooked pasta to the simmering soup. Cook according to the package directions, stirring occasionally, for about 10-12 minutes or until the pasta is al dente and tender.
While the pasta cooks, prepare the cheese mixture by stirring together 8 ounces of ricotta cheese, 1/2 cup of grated Parmesan cheese, and 1/4 teaspoon of black pepper in a small bowl until it is smooth and well-combined.
Turn off the heat under the soup. Stir in 1/2 cup of heavy cream until it is fully incorporated and the soup takes on a creamy, orange hue.
Ladle the hot soup into bowls. Top each serving with a dollop of the ricotta mixture, a generous sprinkle of shredded mozzarella cheese, and a garnish of fresh basil.