Place potatoes in a pot and fill with enough water to cover the potatoes. Bring to a boil and cook until potatoes are tender, about 10 minutes.
Drain potatoes and mash with a potato masher. Add butter, milk, cheese, bacon, and green onions. Mix until combined and season with salt and pepper.
Transfer mashed potatoes to a greased 9x13 inch baking dish. Bake in preheated oven for 20 minutes, or until cheese is melted and potatoes are heated through.
Serve hot.
Interesting Facts
Twice-baked potatoes are a popular comfort food dish.
The dish was originally created in the 1950s by a chef in New York.
The dish is a great way to use up leftover mashed potatoes.