Put flour, hazelnuts, sugar, salt, fat in flakes, egg, orange peel and vanilla sugar in a mixing bowl. Work through with the dough hooks of the hand mixer. With cool hands quickly knead to a smooth dough. Cover and leave to rest in a cool place for about 1 hour. Quarter the dough and form into 4 rolls. Divide into 15 pieces each and roll them into strands of dough about 24 cm long.
Place on two baking trays lined with baking paper and bake in a preheated oven (electric range: 200 °C/ gas: level 3) for 12-15 minutes until light brown. Cool down on a cake rack. Chop the couverture and melt on a hot water bath. Dip the pretzels halfway into the chocolate coating and sprinkle with sugar crystals. Leave to dry. Keep cool in well closed tins