Preheat the oven and prep a dish: Set the oven to 375°F (190°C). Lightly spray a 9x13-inch baking dish with cooking spray.

Cook the pasta: Boil the high-protein pasta in salted water for 1–2 minutes less than package directions. It should be just shy of al dente, since it will cook more in the oven. Drain and set aside.

Sauté the aromatics: Warm olive oil in a large skillet over medium heat. Add onion and bell pepper; cook 3–4 minutes until softened. Stir in mushrooms and cook another 2–3 minutes. Add garlic and cook 30 seconds until fragrant.

Brown the meat: Add ground turkey (or your choice of meat) to the skillet. Season with Italian seasoning, a pinch of salt, black pepper, and red pepper flakes if using. Cook, breaking it up with a spoon, until no longer pink.

Sauce it up: Pour in the marinara or pizza sauce. Let it simmer 2–3 minutes so the flavors meld. Taste and adjust seasoning if needed.

Blend the creamy layer: In a bowl, stir together cottage cheese and half of the Parmesan. Season with a pinch of salt and pepper. For a smoother texture, you can briefly blend the cottage cheese, but it’s optional.

Assemble the casserole: In the prepared baking dish, combine cooked pasta with the meat sauce. Gently fold in half of the mozzarella and half of the pepperoni. Spread the cottage cheese mixture evenly over the top. Sprinkle on the remaining mozzarella and Parmesan. Scatter the remaining pepperoni slices across the surface.

Bake: Cover with foil and bake for 15 minutes. Remove the foil and bake another 10–12 minutes, until the cheese is melted and the edges are bubbling.

Broil for the finish: Switch to broil for 1–2 minutes to brown the cheese lightly. Keep a close eye so it doesn’t burn.

Rest and garnish: Let the casserole rest 5–10 minutes to set. Top with chopped basil or parsley. Slice and serve hot.