Preheat oven to 400 degrees F. Lightly grease with butter 8 – 9 of the wells of a nonstick muffin pan. In a medium mixing bowl whisk the eggs then mix in the sour cream. Stir in both cheeses and the chives. Add potatoes and mix well. Spoon them into the pan filling the cups to slightly below the top. Bake 25- 35 minutes until they pull away from the sides of the cup and are golden brown. Remove from oven and let them cool 5 minutes in pan. Serve with sour cream if desired.