Cook the Pasta Bring a large pot of salted water to a boil. Add the mostaccioli and cook until just shy of al dente—usually about 2 minutes less than the package directions. Why slightly undercooked? Because the pasta finishes cooking in the oven. Drain the pasta and set it aside.

Brown the Meat Heat a large skillet over medium heat. Add the Italian sausage or ground beef and cook until browned, breaking it apart with a spoon. Once the meat is mostly cooked, stir in the diced onion. Cook about 4–5 minutes until softened. Add garlic and cook another minute. Your kitchen should smell amazing at this point.

Build the Sauce Now stir in: • marinara sauce • tomato paste • Italian seasoning • salt and pepper Let the sauce simmer 10 minutes. That short simmer thickens the sauce and blends the flavors. If the tomatoes taste a little sharp, add a pinch of sugar. It balances the acidity beautifully.

Combine Pasta and Sauce Add the drained pasta directly to the skillet with the sauce. Stir gently so every piece of pasta gets coated. Mix in about half of the shredded mozzarella. This step creates that creamy, cheesy interior layer once the casserole bakes.

Assemble the Casserole Preheat the oven to 375°F. Lightly grease a 9×13 baking dish. Spread half of the pasta mixture in the dish. Add a layer of mozzarella and Parmesan. Then top with the remaining pasta. Finish with the rest of the cheese. It may look like a lot of cheese. That’s okay. It’s supposed to.

Bake Place the dish in the oven and bake for 25–30 minutes. You’ll know it’s ready when: • the cheese melts completely • the sauce bubbles around the edges If you like a golden top, broil the dish for the last 2–3 minutes. Just keep an eye on it—cheese browns quickly.

Let It Rest Here’s a small step many people skip. Let the casserole sit 5–10 minutes before serving. Why? The cheese firms up slightly, which makes scooping easier.