Remove the crust from the toast and cut into very small cubes. Cut the vanilla bean in half, scrape out the pulp, keep the pod for later. Drain the curd in a sieve. Peel apple (1), grate coarsely and mix with juice of one lemon (1).
Beat butter (1) with the beaters of a hand mixer until creamy. Gradually beat in egg at the beginning, then the curd, sour cream, flour, salt and vanilla pulp. Then stir in the toast cubes and the grated apple with a spatula. Cover the mixture and let it cool for at least 1/2 hour.
Chop the hazelnut kernels medium fine and roast in a frying pan without fat, turning until golden brown.
For garnish, remove skin from apple (2), cut into quarters, remove core and cut each quarter into 3 wedges. Sprinkle apple slices with the juice of one lemon (2).
Boil the apple juice with the vanilla pod.
Form smooth oval dumplings from the apple dumpling mixture with two tablespoons (3 per person) and shape in the apple juice. Cook in the slightly bubbling apple juice for about 10-12 minutes, turning once to the other side.
In the meantime, foam butter (2) in a frying pan, glaze the apple slices with sugar (1) in it over medium heat for 1 minute on each side.
Beat the egg yolks with the white wine, sugar (2) and cinnamon in a bain-marie or on the automatic plate for about 5 minutes until creamy.
Remove the apple dumplings with a skimmer and drain on kitchen roll.