Set the oven to 200C (400F).
Scrub the potatoes well and prick all over with a
fork. Rub with salt. Place in a baking pan and bake
in the oven for about 50 minutes or until tender.
Remove from the oven, cut in
half, and using a spoon, scoop out the flesh into a
bowl, leaving the skin. Mash the potatoes lightly and
add milk, butter, grated cheese, and sauteed chopped
onion. Stuff the mixture into the skin shell. Top
each with grated cheese, and bake until the cheese
melted.