Set the oven rack to the center position. Preheat to 400ºF (204ºF).
Place a wire rack on top of a foil-lined rimmed baking sheet, set aside.
Scrub and rinse the outside of the potatoes with cool water. Dry with a towel.
Pierce each potato with a fork 8 times, about ⅛-inch deep pricks all around.
Evenly space the potatoes on top of the wire rack.
Lightly brush olive oil over the surface of the potatoes. Sprinkle with salt.
Bake until the center of the potato pierces easily with a fork and registers between 200 to 205ºF (93 to 96ºC), about 60 to 80 minutes depending on size. Meanwhile, cook the bacon.
Add the bacon to a cold large cast iron skillet. Turn heat to medium, cook, stirring occasionally until crispy, about 10 to 12 minutes. Transfer to a paper towel-lined plate to drain.
Remove the potatoes from the oven, and allow to cool until cool enough to touch, 10 to 15 minutes.
Slice each potato lengthwise down the center.
Use a spoon to remove the flesh and transfer to a large bowl. It helps to place the potato in a paper towel to help scoop out the flesh. Make sure to leave about ¼-inch thick shell of flesh around the edges. There should be about 3 ½ cups of flesh.
Place the potato skins cut side up, back on the sheet pan on top of the wire rack and place in the oven for 10 minutes to help dry the shells.
Lightly mash the potatoes with the butter.
Add 1 cup of cheese, sour cream, milk, ¼ cup of green onions, and bacon (reserving 2 tablespoons for topping). Use a spatula to combine the ingredients together.
Fill each potato boat with about ½ cup of filling, shaped into a mound.
Sprinkle about 1 tablespoon of cheese on top.
Broil until the cheese is melted, about 5 minutes.
Top with reserved bacon, green onions, and black pepper, then serve immediately.
Storing and Reheating: Refrigerate covered for up to 3 days. Reheat one at a time in the microwave on “high” setting in 30-second intervals until warmed through, about 1 to 2 minutes.
Freezing: Individually wrap potatoes in plastic, place into a resealable bags, store in the freezer for up to 1 month. To reheat, unwrap and bake at 350°F (177°C) on a wire rack or foil-lined baking sheet until warmed through, about 30 to 45 minutes, checking every 5 minutes.
Make it an appetizer: Use smaller sized potatoes, about 5 to 8 ounces.