Bring a large pot of salted water to a boil. Add the rigatoni and cook according to package instructions until al dente. Reserve 1 cup of pasta water, then drain and set aside.
In a large skillet over medium heat, add the olive oil. Once heated, crumble the sausage into the skillet and cook until browned and cooked through, about 5-7 minutes. Stir frequently to break up the sausage into smaller pieces.
Add minced garlic to the skillet and sauté for about 1 minute until fragrant, being careful not to burn it.
Pour in the heavy cream and vegetable broth, stirring to combine. Allow the mixture to simmer for about 3-5 minutes until it thickens slightly.
Add the chopped spinach to the skillet and cook for another 2-3 minutes until wilted.
Stir in the grated Parmesan cheese until melted and creamy. If the sauce is too thick, add some reserved pasta water until you reach the desired consistency.
Toss the cooked rigatoni into the skillet with the creamy sauce, stirring to coat the pasta evenly. Season with salt, pepper, and red pepper flakes if desired.
Serve immediately, garnished with fresh basil.
Notes
Feel free to adjust the level of spiciness by choosing sweet or spicy sausage.