Paccheri with Quick Sausage Ragu

Ingredients

• pound paccheri pasta
• tablespoons olive oil
• tablespoons butter
• medium red onion, thinly sliced
• garlic, thinly sliced
• tablespoon fennel seeds
• teaspoon chili flakes, optional
• ounces spicy Italian sausage, casings removed
• tomato paste
• tablespoons kosher salt for salting the pasta water, plus more to taste
• pasta water
• heavy cream
• teaspoon freshly grated black pepper
• Freshly grated Parmesan cheese, for serving
• Fresh basil, for serving