Bring a large pot of salted water to a boil. Add the rigatoni and cook according to package instructions until al dente, typically around 10-12 minutes. Drain the pasta and reserve about a cup of pasta water.

In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add the crumbled Italian sausage and sauté for 5-7 minutes until well browned.

Add the diced onion and minced garlic to the skillet. Sauté for an additional 3-4 minutes until the onion is translucent.

Stir in the crushed tomatoes, heavy cream, and chicken broth. Sprinkle in Italian seasoning and red pepper flakes. Season with salt and pepper and bring to a gentle simmer.

Add the cooked rigatoni to the sauce, gently tossing to coat. Add a splash of reserved pasta water if the sauce is too thick.

Remove from heat and stir in the grated Parmesan cheese, mixing until the cheese melts and integrates smoothly.

Spoon the Creamy Italian Sausage Rigatoni onto warm plates and garnish with fresh basil leaves. Serve immediately.