Baked Mashed Potatoes (or Cream Cheese Mashed Potatoes)

cup-a cup-a: A Legacy of Heritage Gifts, Ham Balls and So Much ...:
Baked Mashed Potatoes (or Cream Cheese Mashed Potatoes)
10 medium potatoes, peeled and boiled
1 stick butter
1 tsp. salt
1/4 tsp. pepper
1 Tbsp. grated onion (or I used 1 tsp. dried, minced onion)
1 cup milk, heated
8 oz. cream cheese (at room temperature)

Whip potatoes in butter.  Add remaining ingredients and best until fluffy. (Add more milk if needed). Place in buttered casserole.  Bake for 30 minutes at 350 degrees. Stir once while baking. (May be prepared a day in advance and baked before serving.)