Bring a large pot of salted water to a rolling boil over high heat. Add the 400 g rigatoni pasta and cook according to package instructions until al dente, usually about 10-12 minutes. Stir occasionally to prevent sticking. Once cooked, drain the pasta in a colander, allowing any excess water to escape, and set aside.

In a large skillet, heat 1 tablespoon of olive oil over medium heat. Once the oil shimmers, add the 500 g of Italian sausage, breaking it apart with a spatula as it cooks. Brown the sausage for about 5-7 minutes until no longer pink and slightly crispy, enhancing the dish's texture and flavor.

Add the diced onion and minced garlic to the skillet with the browned sausage. Sauté for about 3-4 minutes, stirring frequently, until the onion becomes translucent and the garlic is fragrant.

Pour in the 400 g can of crushed tomatoes, 1 cup of heavy cream, and 1 cup of chicken broth into the skillet. Stir in 1 teaspoon of Italian seasoning and, if desired, add ½ teaspoon of red pepper flakes for warmth. Season with salt and pepper to taste. Let the sauce simmer for about 10 minutes.

Once your sauce is beautifully simmered, add the drained rigatoni to the skillet. Gently stir to coat all the pasta in the creamy sauce.

Sprinkle ½ cup of grated Parmesan cheese over the pasta and stir until the cheese is fully melted and the sauce becomes smooth and creamy.

Serve your Creamy Italian Sausage Rigatoni hot, garnished with fresh basil leaves for a pop of color and flavor.