Crumble the rusks, pour milk over them and let them steep. Meanwhile, cut the peeled apples finely and layer them in a greased casserole dish.
Foam mixture: Mix together butter, sugar, egg yolk and lemon (or cinnamon). Add the soaked rusks. Fold in the whipped egg whites. Cover the apples with the egg foam. Bake at 175-195 degrees for about 15-50 minutes.