For the cheesy potatoes, boil, peel and slice the potatoes. Prepare a béchamel sauce. Melt butter in a pan and add flour and pour in milk.
Mix in the egg yolks and diced cheese and stir in the sour cream. Season with salt, pepper and nutmeg.
Mix in the sliced potatoes. Beat egg whites until stiff and fold into potatoes.
Grease casserole dish with butter and pour in potato mixture. Sprinkle with some grated cheese and breadcrumbs and pour melted butter.
Bake the cheese potatoes for about 3/4 hour at 170°C.