Cook the Pasta: Prepare penne pasta according to package directions until al dente. Drain and set aside.
Brown the Sausage: In a large skillet, heat the olive oil over medium heat. Add the sausage, breaking it up with a spoon, and cook until browned, about 5-7 minutes.
Add Garlic and Spinach: Stir in minced garlic and cook for 1 minute until fragrant. Add fresh spinach and cook for 2-3 minutes until wilted.
Create the Creamy Sauce: Pour in the heavy cream, stirring until combined. Gradually add the grated Parmesan cheese, stirring until melted and the sauce becomes creamy.
Season and Combine: Season with salt, pepper, and red pepper flakes, if using. Add the cooked penne to the skillet, stirring to coat the pasta evenly in the creamy sauce.
Serve: Serve warm, garnished with extra Parmesan cheese if desired.