Heat the butter in the pan and steam the grated apple in it until translucent. Season with salt, pepper and sugar. Then deglaze with the orange liqueur.
Whisk the eggs and stir into the apple mixture. Let it set a little and then distribute it on the white bread slices.
Sprinkle with breadcrumbs and top each with a slice of cheese.
Baked in the oven for about 5 minutes until the bread has got a nice golden brown color.