Wrap each potato in aluminum foil and bake until tender, about 1 hour.
Remove potatoes from oven, let cool slightly, then cut in half lengthwise. Using a spoon, gently scoop out the flesh from the center of each potato, leaving a border to maintain their shape.
In a bowl, combine the potato flesh, half the chopped smoked meat, 4 slices of cheese cut into chunks, butter or sour cream, salt and pepper.
Fill the hollowed-out potatoes with this mixture and arrange the remaining cheese slices on top.
Place the potatoes on a baking tray covered with parchment paper or a silicone mat, and bake until the cheese has melted and turned golden.
Meanwhile, heat the remaining smoked meat in a skillet or microwave oven.
Remove potatoes from oven.
Spread hot smoked meat, a drizzle of sweet mustard and a few fried onions on each potato. On each garnished potato, spread hot smoked meat, a drizzle of sweet mustard, and a few fried onions.
