Creating the magnificent Creamy Sausage Pasta is simple if you follow these detailed steps:

1. Cook the Pasta: In a large pot of salted boiling water, cook the penne pasta according to package instructions until al dente. Drain and set aside.

2. Brown the Sausage: In a large skillet, heat the olive oil over medium heat. Add the Italian sausage, breaking it apart with a spatula. Cook until browned and cooked through, about 5-7 minutes.

3. Sauté the Vegetables: Add the diced onion to the skillet, and sauté until soft and translucent, about 3-4 minutes. Stir in the minced garlic and cook for an additional 1 minute, being careful not to burn it.

4. Add Liquid Ingredients: Pour in the chicken or vegetable broth and heavy cream. Stir well to combine everything.

5. Combine Pasta and Sauce: Add the cooked pasta to the skillet, mixing well to ensure that the pasta is well coated with the sauce.

6. Season: Stir in the grated Parmesan cheese, Italian seasoning, and red pepper flakes (if using). Season with salt and black pepper to taste. Allow the mixture to simmer for about 2-3 minutes to let the flavors meld.

7. Garnish and Serve: Once the sauce thickens slightly, remove from heat. Garnish with fresh parsley before serving.

By following these steps, you will master the art of making a creamy, flavorful dish that is as satisfying to prepare as it is to eat!