Preheat the oven to 400 degrees F.
Then, wash and dry the potatoes. It is very important to pat them dry.
Place the potatoes on a baking sheet. Rub them with some olive oil, sprinkle with salt and bake for about 50 minutes. The potatoes should be tender inside if you poked with a fork. Remove the potatoes from the oven. Lower the heat to 350 degrees F.
With a sharp knife, cut each potato in half lengthwise. Scrape out the insides into the mixing bowl, being careful not to tear the shell. Leave a small rim of potato intact for support, about 1/4 inch of flesh on the sides. Lay the hollowed out potato shells on a baking sheet covered with parchment paper.
Add the scooped potato interiors to a large mixing bowl. Add milk, sour cream, minced garlic, chopped green onions, bacon bits and softened butter, stir well to combine.
Add the cheeses, season with salt and black pepper to taste and mix together well.
Fill the potato shells with the filling, and sprinkle some more grated cheese on top.
Put them back in the oven for another 15-20 minutes at 350 degrees F.
Serve with extra toppings if desired: chopped green onion, chives, bacon crumbs and sour cream.