Peel and grate potatoes (food processor works well), and drain off liquid.

Sauté the bacon and onion.

Pour scalded milk over the potatoes, add pepper, salt, onion, bacon (broken to small pieces) and egg yolks. Mix well.

Fold in beaten egg whites. Pour into a greased 9x13 roasting pan.
Bake at 450 degrees F. for 15 min and then lower heat to 400 degrees F. for another half hour. When done, slice into oblong pieces; serve with sour cream.