Wash the potatoes well and boil them for about 35 to 40 minutes. You can also do this in the microwave (first potato= 8 minutes, 2nd= 8 minutes, 3rd= 4 minutes, 4th= 4 minutes, so all 4 potatoes should be in the microwave for around 25 minutes; remember to poke the potatoes with a fork before placing them in the microwave, so they don't explode!) Once the potatoes are soft, cut them in halves and scoop out the center of each potato. Save that in a bowl, we'll need it later. Sprinkle salt and pepper on the potato skins.
Take the chopped bacon and fry it for about 7 minutes. Mix the remaining of the potatoes (the ones you put in a bowl), butter, mustard, shredded cheese, milk, garlic, salt, and pepper and mix well. You can also use a blender or food processor for this. Add this mix to the inside of the potatoes and sprinkle the bacon pieces on top, place them in a deep dish or tray and cover with aluminum foil. Bake for 15-20 mins at 355F