I adapted this recipe from the Victory Garden Cookbook. It has lots of great recipes for all sorts of vegetables.
Step 1: Cook the Squash
You can peel it, then boil or steam it until soft.
You can also put it in the oven whole, or cut in half and take out the seeds. Then cook it until it's tender. If you cook it whole, when it's done, cut it in half and remove the seeds with a spoon. Then you can scoop out the flesh.
The only problem with cooking butternut whole is the body cooks way faster than the neck, since it's hollow.
You could also used canned or frozen squash.