Place potatoes in a saucepan, and cover with salted water.
Bring to a boil over med-high heat.
Cook until tender, then drain well.
Preheat oven to 375Â° degrees F.
Put the cooked potatoes in your mixer and add cream cheese, sour cream, butter, milk, salt and pepper.
Whip till smooth.
Stir in 1 cup of the cheese and half the bacon.
Spoon mixture evenly into a lightly oiled 3-quart casserole dish.
Bake for 20 minutes.
Top with remaining cheese, bacon and green onions.
Bake for 5 more minutes to melt cheese. Serve this yummy twice baked potato casserole immediately!