Slice your potatoes in half and hollow out the centre to leave a skin (save the flesh for another time). Brush with butter and bake for 10 minutes at 200°C.
Meanwhile, fry your pepper and onion in the oil over a medium-high heat. Once wilted and a bit coloured, push to one side and add the steak. Fry without moving too much- season with the spices, salt and pepper. Remove from the heat.
Fill each skin with a little cheddar, then steak mix, a bit more cheddar and some slices of provolone.