4 c. hot mashed potatoes prepared as you serve them
1 (8 oz.) pkg. cream cheese, room temp.
1 egg, beaten
1/4 c. chopped onion (optional)

Put in casserole and bake 45 minutes at 350 degrees. If you double batch, put in 2 separate dishes or otherwise it will puff up.

This may be made ahead (even the day before) and baked later. Allow a little longer baking time. Serves 8.