1-First Step: Prep the oven and baking dish Start by preheating your oven to 350 degrees Fahrenheit. Spray a 9×13-inch baking dish with nonstick cooking spray so nothing sticks later. This small step makes cleanup much easier. While the oven heats, gather your ingredients so everything is ready to go.

2-Second Step: Cook the spaghetti Bring a large pot of water to a boil and cook the spaghetti noodles according to the package instructions until al dente. You want the pasta to still have a little bite because it will continue cooking in the oven. Before draining, reserve 1/4 cup of pasta water. That little splash can help loosen the sauce later if it gets too thick.

3-Third Step: Make the Alfredo sauce Set a skillet over medium-high heat and melt the butter. Add the minced garlic and cook for about 30 seconds, just until fragrant. Be careful not to let it brown too much because garlic can turn bitter fast. Next, whisk in the heavy whipping cream and cook until the sauce thickens slightly. Take the skillet off the heat and season the sauce with salt and pepper. Stir in the grated parmesan cheese until smooth and creamy. If the sauce feels too thick, add a little reserved pasta water to loosen it. The goal is a sauce that coats the noodles nicely without turning watery.

4-Fourth Step: Toss the pasta with the Alfredo sauce Add the cooked spaghetti to the Alfredo sauce and toss until every noodle is coated. This is where the dish starts to feel extra comforting. Make sure the noodles are evenly covered so every bite tastes creamy and rich. Then spread the Alfredo-coated spaghetti into the prepared baking dish.

5-Fifth Step: Cook the sausage and make the meat sauce In another skillet, cook the Italian sausage over medium heat until browned. Break it apart as it cooks so you get even pieces throughout the casserole. Once it is cooked, drain any excess grease. Stir in the jar of spaghetti sauce and let everything mingle for a minute or two. This creates a savory tomato meat sauce that sits beautifully on top of the cream layer. If you like more tomato flavor, let the sausage sauce simmer gently for a few extra minutes before layering it in. That can deepen the flavor a bit more. If you are making a pasta night and want another creamy family dinner, this creamy chicken and broccoli pasta is another nice option.

6-Sixth Step: Build the casserole Carefully spread the sausage and spaghetti sauce mixture over the Alfredo spaghetti layer. Try to cover the pasta as evenly as possible so every scoop gets some of both sauces. Then sprinkle the shredded mozzarella cheese all over the top. The cheese will melt into a golden, bubbly blanket in the oven.

7-Final Step: Bake and serve Bake the casserole for 25 to 30 minutes, or until it is bubbly and the mozzarella is melted. If you want a prettier finish, let it rest for a few minutes before serving. Garnish with fresh basil or parsley for color and a fresh flavor boost. The herbs make the dish look finished and give each serving a little brightness.