1. Peel and cube a butternut squash, reserving the seeds and measuring out approximately 3 1/2 cups.
2. In a large saucepan, melt the butter and add the garlic and onion, sautéing until the onion is soft and translucent, approximately 5 minutes. Add the cubed squash and fry for 4-5 minutes. Add the broth and bring to a boil. Simmer the squash for 15-20 minutes, covered, or until the squash can be easily pierced with a fork.
3. While the squash is simmering, begin boiling the water for the pasta. Cook the pasta for 8-10 minutes or until al dente. Rinse and drain.
4. Preheat the oven to 400 F and line a baking sheet with parchment paper. Place the prosciutto in a single layer on the baking sheet. Bake the prosciutto for 8-10 minutes, or until crisp. Set aside. This is also when I typically roast the squash seeds, for about 10 minutes, while the oven is still hot.
5. Using an immersion blender or a regular blender in small batches, blend the squash and broth  mixture until most large chunks are pureed. Return the sauce to the sauce pan over low heat, and slowly stir in the milk, followed by the cheese. Add the drained pasta and toss to combine. Crumble the baked prosciutto over the top of the dish and serve, topping with roasted butternut squash seeds if desired.

Leftovers can be kept in an airtight container, sealed, in the fridge for 3-4 days.