Peel and cut the Golden Delicious apples in large julienne slices
Mince the red cabbage and blanch it for 2 minutes in salted boiling water
Slice the onions, sweat them in butter over low heat for about 8 minutes, season then add the sliced apples and the blanched cabbage. Cover with baking paper and cook for 20 minutes on low heat, don't forget to check the seasoning.
Peel and grate the raw potatoes, season with salt, pepper and a rasp of nutmeg. Cook the grated potatoes in circles of 13 cm in diameter in clarified butter and a block of duck fat over a thickness of 1/2 cm: the apples must be crisp and golden on both sides but remain soft inside.
Assembly
Cut the burger buns in half, horizontally, and keep the top as a hat.
Arrange on the lower bun: the apple slab, the warm chopped gizzards, red cabbage with apple, the rocket seasoned with honey-walnut vinaigrette, the slices of smoked duck breast, finish with the shavings of foie gras and cover with the bun hat.