Loaded Twice Baked Mashed Potatoes

3 medium potatoes or 4 small potatoes
3/4 c milk
2 tbsp butter
1/4 c sour cream
1/4 c cream cheese
1/2 c shredded mozzarella cheese
1/4 c shredded cheddar cheese
1/4 tsp salt
1/4 tsp pepper
1/4 tsp chives
1/2 c chopped cooked bacon
optional: 2 tbsp bacon bleu cheese compound butter (I made this last week for chicken and had some left over- see Bacon Bleu Cheese Chicken)

Preheat oven to 425.  Thoroughly clean baked potatoes and prick all over with a fork.  Place on a baking sheet and bake for 40-60 minutes or until potatoes are cooked through.  Once cooked, chop into chunks.  Place the potatoes in a large bowl (skins and all).  Add milk.  On medium speed, use hand mixer to blend together.  Add butter, sour cream, and cream cheese (and compound butter if desired) and blend.  Add seasonings, cheese and bacon.  Mix with a spoon.  Spoon into a 1 1/2 quart baking dish and bake for 15 minutes.