Peel and core the apples and slice them into slices of uniform thickness. Sprinkle with rum, vanilla and sugar and let stand for at least a half an hour. Melt the butter and mix with the lukewarm milk, egg yolks, a dash of grappa, the flour and a pinch of salt into a thick batter. Let rest for more than an hour. After resting the batter, whip the egg whites until stiff and fold into the batter. Heat the peanut oil in a pan, batter the apple slices and fry them on both sides in the hot oil until golden brown. Dust with cinnamon-sugar and serve while hot.