1. In a large skillet, cook sausages over medium-high, breaking up meat with a spoon, until browned, 5 minutes. Transfer 4 cups leeks to an airtight container and refrigerate for later use. Add remaining leeks (4 cups) to sausage in skillet and cook until softened, 5 minutes. Add wine and cook, stirring frequently, until mostly evaporated, 2 minutes. Stir in butter and season to taste with salt and pepper.

2. Meanwhile, in a large pot of boiling salted water, cook pasta according to package instructions. Reserve 1/2 cup pasta water. Drain pasta, return to pot, along with sausage mixture, and toss to combine. Add lettuce and enough pasta water to create a light sauce that coats pasta. Toss to combine. Serve with Parmesan on the side.