This sausage and butternut squash pasta uses leftover cooked sausage, making it what Rach calls a "rollover" meal.
Bring a large pot of salted water to a boil and add the pasta. Cook to al dente according to package directions.
In a sauté pan, melt the butter over medium-high heat. Add shallot and garlic, and sauté until fragrant, about 1 minute. Add the flour and stir for a minute or two. Using a whisk, slowly mix the milk into the flour mixture. Once smooth, stir in the chicken stock and white wine vinegar. Add the parmesan and season with salt and pepper. Once smooth, transfer to a blender and add the roasted squash and roasted pears. Blend until smooth. If you need to thin the sauce a bit, add some of the pasta cooking water until desired thickness.
Pour the sauce and the pasta into a pot or large bowl and toss in the cooked, sliced sausage.