Bake potatoes at 375° for 1 hour or until tender. When cool enough to handle, cut a thin slice off the top of each potato; scoop out pulp, leaving a thin shell. In a bowl, mash the pulp, egg, milk, mayonnaise, 1/2 cup of cheese, salt and pepper. Spoon into potato shells. Top with onion, bacon and remaining cheese.
Place in a small ungreased baking pan.
Bake, uncovered, at 375° for 25-30 minutes or until heated through.
