I like to make the puree with the butter and milk. You don't have to but the bread just comes out so moist. Be sure to grease the pans well it has a tendency to stick. I use Crisco and not spray because it gives it a nice golden crust and the spray seems to stick.
First make the puree. Peel squash and remove seeds. Dice the squash and add it to boiling salted water. When the squash is soft drain. Add the 1/4 stick butter and just enough milk to make it a smooth consistency. Set aside 1 and 1/2 cups for the bread. Save the rest for a side dish for dinner.
Preheat oven 325 degrees.
Cream butter and gradually add the sugar. Beat adding one egg at a time.
Beat in the remaining ingredients except vanilla and nuts.
Stir in vanilla and the nuts if you are using them.
Generously grease to bread pans. Divide the bread mix equally in both pans.
Bake for 1 hour. Let cool. Remove from pans and serve.