Core, quarter and pare the apples; shred. Beat egg yolks, sugar, flour, nutmeg and calvados into apples. Beat egg whites stiff, fold into apple mixture. Heat butter in non-stick skillet; add the apple mixture and saute over medium heat until bottom of the omelet is browned ( 2 or 3 minutes ). Turn the omelet and brown other side. Slip omelet onto a warm plate and sprinkle with confectioner's sugar.