Place potatoes in saucepan, and cover with salted water. Bring to a boil over med-high heat. Cook until tender, then drain well.
Preheat oven to 375° degrees F.
Transfer potatoes back to the saucepan. Masher with a potato masher until almost smooth. Add cream cheese, sour cream, butter, milk, salt and pepper. Continue mashing until smooth. Stir in 1 cup of the cheese and half the bacon. Spoon mixture evenly into a lightly oiled 3-quart casserole dish. Use a spatula or fork to make an irregular surface (see photo).
Bake for 20 minutes. Top with remaining cheese, bacon and green onions. Bake for 5 more minutes to melt cheese. Serve immediately.