Bring a large pot of salted water to a rolling boil. Add the pappardelle pasta and cook according to package directions until al dente. Before draining, reserve about 1/2 cup of the starchy pasta water. Drain the pasta and set aside.

In a large skillet or Dutch oven, heat the olive oil over medium-high heat. Add the ground Italian sausage and cook, breaking it apart with a spoon, until browned and cooked through. Drain any excess grease. Add the finely chopped onion to the skillet and cook for 3-5 minutes until softened. Stir in the minced garlic and red pepper flakes, and cook for another minute until fragrant.

Add the diced tomatoes (undrained) and dried oregano to the skillet. Stir well to combine. Pour in the chicken broth and bring the mixture to a simmer. Reduce the heat to low, cover, and let the sauce simmer for 10-15 minutes, allowing the flavors to meld and deepen. This step is crucial for developing the rich taste of the sauce.

Uncover the skillet and stir in the heavy cream. Bring the sauce back to a gentle simmer. Gradually stir in the grated Parmesan cheese until it is fully melted and the sauce is smooth and creamy. If the sauce is too thick, add a tablespoon or two of the reserved pasta water until it reaches your desired consistency. Taste and adjust seasoning with salt and freshly ground black pepper as needed.

Add the cooked and drained pappardelle pasta to the skillet with the creamy chili sauce. Toss gently to coat the pasta evenly. If the sauce seems too thick, add a little more reserved pasta water. Serve immediately, garnished with fresh chopped parsley or basil and extra grated Parmesan cheese, if desired. Enjoy this comforting and flavorful meal!