Bring a large pot of salted water to a boil. Cook the pappardelle according to package instructions until al dente. Reserve 1/2 cup of pasta water, then drain the pasta and set aside.
In a large skillet, heat the olive oil over medium heat. Add the Italian sausage, breaking it up with a spoon. Cook until browned and cooked through, about 5-7 minutes.
Add the diced onion and sliced fennel to the skillet. Sauté for about 5 minutes, or until the vegetables are softened. Stir in the minced garlic and Calabrian chili paste, cooking for an additional minute until fragrant.
Pour in the heavy cream and bring to a gentle simmer. Stir in the grated Parmesan cheese and mix until melted and combined. If the sauce is too thick, add some reserved pasta water to reach desired consistency.
Add the cooked pappardelle to the skillet, tossing to coat the pasta in the creamy sauce. Season with salt and pepper to taste.
Serve immediately, garnished with fresh parsley and additional Parmesan if desired.