Separate the egg. Cover the egg white and chill. Briefly mix flour, cold butter in pieces, sugar, vanillin sugar, salt, egg yolk and 4-5 tablespoons of cold water with the dough hooks of the hand mixer. Pour onto the work surface and knead into a smooth dough with your hands. Wrap in cling film and chill for 1 hour. Roll out dough 1/2 cm thin on a floured work surface.
Cut out rabbits (8 cm high) and place them on 3 baking trays lined with baking paper. Roll out the rest of the dough again. Cut out further rabbits. Bake the trays one after the other in a preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: level 2) for about 15 minutes. Let the biscuits cool down. Mix egg white, icing sugar and lemon juice with the whisk of the hand mixer. Leave 1/4 of the icing white. Colour the rest of the icing orange with red and yellow food colouring. Put the white icing in a small piping bag or freezer bag. Cut off a small corner. Spread the biscuits with orange icing.
Mix egg white, icing sugar and lemon juice with the whisk of the hand mixer. Leave 1/4 of the icing white. Colour the rest of the icing orange with red and yellow food colouring. Put the white icing in a small piping bag or freezer bag. Cut off a small corner. Spread the biscuits with orange icing. Leave to dry. Decorate rabbits with white icing and sugar pearls