Step 1Preheat oven to 375ยฐ. In a medium bowl, whisk eggs, mozzarella, and cream; season with salt, black pepper, and red pepper.
Step 2In a large ovenproof skillet over medium heat, heat oil. Add shallot and garlic and cook, stirring occasionally, until shallot is translucent, about 5 minutes. Add mushrooms and cook, stirring occasionally, until softened, about 5 minutes more. Add spinach and cook, stirring frequently, until wilted, about 2 minutes; season with salt and black pepper.
Step 3Pour egg mixture into pan over vegetables. Dollop with ricotta.
Step 4Bake frittata until eggs are just set and edges are golden brown, about 12 minutes.