Instructions:
- Preheat oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish with olive oil.
- If using pasta, boil according to package directions until al dente (slightly undercooked). Drain well and toss in a large mixing bowl with 1 Tbsp olive oil. Set aside. (If using bread cubes, skip boiling; toss cubes with oil.)
- Brown the sausage/meat in a large skillet, breaking it up well. Drain excess grease. Add onion, garlic, and mushrooms; sauté until softened (about 5 minutes). Stir in oregano, salt, and pepper.
- In the mixing bowl containing the pasta/bread, add the entire jar of marinara sauce, the water/stock, Italian seasoning, and red pepper flakes. Stir until the base is evenly coated. If using pre-cooked meat/veg, fold them in now.
- Spread half of the sauced mixture evenly into the prepared baking dish. Sprinkle 1/2 cup of the mozzarella/provolone mix over this layer, followed by half of the pepperoni slices.
- Top with the remaining pasta mixture. Sprinkle the remaining mozzarella/provolone blend evenly over the top layer, followed by the remaining pepperoni and the grated Parmesan cheese.
- Bake for 30–35 minutes, or until the sauce is bubbling vigorously and the cheese topping is melted and golden brown.
- Let the casserole rest for 10 minutes before slicing. Garnish generously with fresh basil before serving.