Wash potatoes and bake at 400°F for 60-70 minutes. When done, slice a small portion off the top and scoop out the pulp leaving 1/4 inch shell. In a bowl, mash the potato that you just removed with the butter, 1/2 tsp salt, pepper and milk. Set aside. In a saucepan, over medium heat, brown beef and onion; drain and cool ten minutes. Add bacon, sour cream and remaining salt. Spoon into potato shells. Top each with a fourth of potato mixture. Sprinkle with cheese. Place potatoes on an ungreased baking sheet and bake at 400°F for 20 - 25 minutes. Makes 4 servings.