Mix flour, salt, sugar, baking powder and vanillin sugar in a bowl. Add egg and butter in pieces. Quickly knead to a smooth dough. Finely chop the candied oranges and knead into the dough.
Cut the dough in half. Form into a roll (approx. 36 cm long, approx. 3 cm Ø). Wrap in foil and chill for at least 2 hours. Cut each roll of dough into approx. 1 cm thick slices. Distribute on about 3 baking trays lined with baking paper. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) one after the other for 10-12 minutes. Let them cool down.