Preheat your oven to 425°F and line a baking sheet with parchment paper.
In a medium bowl, combine the shredded chicken, beaten egg, Parmesan cheese, oregano, garlic powder, salt, and pepper until the mixture holds together when pressed.
Transfer the chicken mixture to the prepared baking sheet and press it into an 8-inch circle about 1/4-inch thick, ensuring the edges are slightly thicker to form a crust.
Bake the crust for 15 minutes until it is firm to the touch and lightly golden around the edges.
Remove the crust from the oven and spread the marinara sauce evenly over the top, then sprinkle with mozzarella cheese and arrange the pepperoni slices.
Return the pizza to the oven and bake for another 8-10 minutes until the cheese is fully melted and bubbly.
Remove from the oven, let it rest for 2-3 minutes to set, then garnish with fresh basil before slicing and serving.