In a mixing jug, add Butter (1/4 cup) and Milk (2/3 cup). Heat in the microwave until melted.
In a mixing bowl, add cooked Potato (2 pound). Pour in the butter and milk mixture a bit at a time, mashing the potatoes as you go.
Place the Bacon (8 slice) in a cold skillet and cook over medium heat until crispy. Remove the bacon from the skillet and drain on paper towels. Chop the bacon and set aside.
Add Sour Cream (2/3 cup), Sharp Cheddar Cheese (5 ounce), Scallion (1/2 cup) and Bacon. Mix until well incorporated. Season with Salt and Pepper (to taste).
Transfer mixture to a baking pan and even out the surface. Top with extra cheese and bacon.
Bake at 400 degrees F (200 degrees C) for 20 minutes.
Top with extra green onions. Serve and enjoy!