Preheat oven to 350 degrees.

 1 medium onion, chopped
 2 tablespoons butter or margarine
 1/2 cup (plus 1/4 cup) grated Cheddar cheese
 1/2 teaspoon salt
 1 can condensed cream of chicken soup
 1 cup sour cream
 1/2 cup butter or margarine
 3 eggs, slightly beaten
 3 pounds sliced yellow squash, cooked until very soft and mashed
 1 1/2 cups (plus an extra 1 cup) buttery cracker crumbs
 1/2 cup butter or margarine, melted

Wash and slice squash. Place in pot, cover with water and boil until soft. Drain well and set aside. Place margarine in a skillet, heat up and sauté the onion in it. In a mixing bowl, combine the sautéed onion, 1/2 cup cheese, salt, soup, sour cream, butter and eggs. Mash
the squash and mix with 1 1/2 cups cracker crumbs. Add the squash mixture to the first mixture and stir to mix. Pour into a greased 9 x 12-inch baking dish or casserole. Bake for 25 to 30 minutes. Mix the remaining 1 cup cracker crumbs with the 1/2 cup melted butter
or margarine. Remove casserole from the oven, and top with the remaining 1/4 cheese and 1 cup buttered cracker crumbs. Return to the oven just long enough to brown the cracker crumbs and melt the cheese.