Knead dumpling dough, egg yolk and 3 tbsp. flour. If the mixture is too moist or not yet formable, knead in a spoonful of flour. Form the mixture into rolls of about 2 cm thickness on a floured work surface.
Cut with a knife into 5-6 cm long trapezoidal pieces (results in about 24 croquettes). Mix the hazelnuts with 1⁄2 tsp. salt, spread on a plate. Whisk eggs with milk in a deep plate.
Pull the croquettes through the egg mass, then turn in the hazelnuts. Press the nuts a little bit and form croquettes if necessary. Heat the oil in a tall large pan. Fry the croquettes in it in portions for approx. 6 minutes, turning them more often.
Drain briefly on kitchen paper. Keep warm in the oven (with the goose) until all croquettes are fried.