Squash Soufflé

3 lbs. yellow squash, diced
1 stick butter or margarine, softened
1 can evaporated milk
3 eggs, beaten
2 tsp. Flour
4 tsp. Salt
¼ cup sugar
1 rounded tbsp. baking powder
1 tsp. Pepper
1 small onion, chopped

In a covered pot, cook squash in a small amount of water until tender, but not mushy. Drain well. Place in a bowl, and mash lightly. Add butter. In a separate bowl, combine remaining ingredients. Add squash mixture, and stir well. Pour mixture into buttered 9" x 12" baking dish, and bake at 350º F for 30 minutes.