Peel and quarter Russet Potato (3.5 pound). Place in a pot, and cover with salted water. Bring to a boil over medium-high heat. Cook until tender, then drain well.
Preheat oven to 350 degrees F (180 degrees C).
Transfer potatoes to a saucepan. Mash with a potato masher until almost smooth. Add Cream Cheese (1/2 cup), Sour Cream (1/2 cup), Butter (4 tablespoon), Milk (1/4 cup), Salt (1 teaspoon) and Ground Black Pepper (1/2 teaspoon). Continue mashing until smooth.
Stir in Cheddar Cheese (1 cup) and Bacon (4 slice)
Spoon mixture into a lightly oiled 3-quart casserole dish. Use a spatula to spread into the dish and make an irregular surface.
Bake for 20 minutes in preheated oven.
Top with remaining Cheddar Cheese (1/2 cup), Bacon (4 slice), and Scallion (1/2 bunch). Bake 5 more minutes to melt cheese. Serve and enjoy!