Squash Casserole

4 cups cooked yellow crook neck squash
1 medium onion
1 Teaspoon salt
1/2 Teaspoon pepper
1 stick butter or margarine
2 cups crushed Cheez-it crackers
2 cups shredded cheddar cheese
1 cup milk or heavy cream

Cook the squash, onion, butter, salt and pepper until onion and squash are tender. Mix remaining ingredients except for 3/4 cup of the crackers and 3/4 cup of the shredded cheese. Pour into a 2 quart casserole and top with remaining crackers & cheese. Bake at 350 for 30 minutes.