prick the potatoes all over and bake in a hot oven (200˚C) for 1 - 1 1/2 hours until tender. turn a couple of times.
cut the potatoes in half and scoop out the flesh carefully with a spoon. return the shells to the oven for a couple of minutes to crisp up.
press the potato flesh through a ricer or mash until smooth. in a large bowl, combine the mashed potato with egg yolks, cheese, butter, cream and parsley. season with salt and pepper.
whisk the egg whites until stiff and carefully fold them into the potato mixture.
fill the shells with the mixture and bake uncovered for 20 -25 minutes until starting to brown on top.