Start by heating olive oil in a 3-quart sauté pan over medium-high heat. Add the Italian sausage, breaking it into small pieces. Cook until golden brown and slightly caramelized, then remove from the pan and set aside.
Reduce the heat to medium and melt butter in the same pan. Add diced onion and fennel, cooking until soft and lightly caramelized. This builds a sweet, aromatic base for the sauce.
Add finely chopped garlic and cook for just 30 seconds. Stir in the tomato paste and Calabrian chili, letting them cook together for about a minute to release their flavors.
Pour in the white wine, letting it simmer for 2 minutes. This lifts the flavorful browned bits from the pan and adds a subtle acidity that balances the creaminess.
Add the tomato purée, heavy cream, fresh oregano, and cooked sausage back to the pan. Stir in a cup of pasta water to loosen the sauce and simmer gently for about 5 minutes, allowing all the flavors to meld together.
Meanwhile, cook pappardelle in heavily salted boiling water until al dente. Drain and return the pasta to the pot. Pour the sauce over the pasta and toss thoroughly to coat every strand.
Gradually stir in freshly grated Parmesan until the sauce clings beautifully to the pasta. Adjust the consistency with pasta water if needed, and season with freshly cracked black pepper before serving.