Scrub potatoes and coat with a small amount of oil. Microwave for 6-8 minutes, flipping halfway through. They are ready when you can easily pierce to the middle with a paring knife. Pick potato up with towel. Cut the top lid off the potato, using a paring knife. Using a small spoon, scoop out the insides into a bowl. Leave enough skin so that the potato still stands by itself. Season the inside of the skin with salt & pepper. Add the lid (top side down) to the inside of the potato. Season with salt & pepper. Mash potatoes with butter, onion, salt & pepper, 1/2 of the cheese, sour cream, & bacon. Taste for seasoning and add in egg yolk. Spoon potatoes until full. Add remaining cheese. Spoon remaining mixture on top of cheese. Bake in a preheated 400F degree oven for 25-30 minutes.