Place butternut squash cubes in a pot with a little bit of water and cook over medium heat, covered, until soft, about 10 minutes (longer if your cubes are big).
Drain most of the water and mash or puree the squash. You can do this with a potato masher, a fork or a food processor.
Bring a large pot of water to a boil. Add salt and cook the pasta according to package directions.
Drain pasta and return pot to the stove.
Over medium heat, melt butter and whisk in the the flour. Keep stirring for 3-4 minutes until the mix looks puffy. Don't let it get dark.
Add the milk slowly, stirring constantly. Keep stirring for a few minutes until the sauce has thickened. Stir in cheeses and squash puree, and cook over low heat until cheese is melted.
Add cooked pasta to the sauce and adjust seasoning. If you don't want to bake your mac and cheese, you can eat it as is.
If you want to bake your mac and cheese, pour the mix into a greased baking dish.
In a small bowl, mix breadcrumbs and oil with your fingers and sprinkle over the pasta mix. Bake at 375 degree for about 20 - 30 minutes.
*Butternut squash options: The recipe above is written for raw butternut squash. You can use leftover pureed butternut squash, cook your butternut squash in the microwave or bake it in the oven. You will need about 2 cups mashed cooked squash.