Step 1

Place the squash, milk, water, and salt in a large pot and bring to a simmer over medium-high heat. Reduce the heat to medium, cover, and cook until the squash is tender, about 20 minutes. (If using frozen squash, it will be tender by the time it comes to a simmer, so cook it uncovered.) Turn off the heat and set aside. Meanwhile, cook the pasta.

Step 2

Bring another large pot of salted water to a boil over high heat. Add the pasta and cook according to the package directions until al dente, 6 to 8 minutes. Drain the pasta and set aside.

Step 3

Use an immersion blender to purée the milk and squash into a smooth sauce. Stir in the nutmeg and pepper. Add the cooked pasta, cheddar, Parmesan, and cream cheese, and stir until the pasta is evenly combined and the cheeses are melted.