Cut squash in half lengthwise.
Remove seeds and place cut sides up, in a baking pan with 1 inch water.
Bake, uncovered, at 350°F for 1 hour.
Cool slightly and remove pulp from shells.
Mash pulp with sugar, eggs and butter.
Stir in nuts.
Spoon into a greased 2 1/2 quart casserole dish.
Bake uncovered at 350°F for 45 to 50 minutes.