First of all, crumble the rusk with your hands into small crumbs and pour over oat drink. Let it steep for 5-10 minutes, so that the oat drink softens the rusk. Separate the egg and beat the egg white until it’s stiff. Mix the egg yolk with butter, cinnamon and maple syrip until foamy. Stir in the softened rusk. Then add the egg white. Peel the apple, cut it in half, core it and slice it into thin slices. Afterwards the apple slices have to be spread in the baking dish (20 x 30 cm). Pour the egg-rusk-mass evenly above the apples and leave the baking dish in the preheated oven (180 degrees) for 30 minutes.