Cut the vanilla pod in half lengthwise and scrape out the pulp with a knife. Knead 250 g flour, sugar, poppy seed, butter and vanilla pulp to a smooth dough. Wrap in foil and chill for about 1 hour.
Preheat oven (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer). Line a baking tray with baking paper. Roll out the dough on a floured work surface to a thickness of approx. ½ cm. Cut out approx. 30 cookies with a fir tree cutter (7 cm) and place on the baking tray. Knead the dough again, roll out and cut out until the dough is used up. Bake the cookies in a hot oven on the lowest shelf for about 12 minutes. Take them out and let them cool down on a cake rack.
Wash the orange with hot water, dry and rub the peel. Halve the fruit, squeeze out one half. Mix icing sugar and 4-5 tablespoons of juice to a smooth glaze. Remove 3 tablespoons of icing, mix with orange peel and fill into a piping bag. Spread the rest of the icing evenly on the biscuits. Cut off the tip of the piping bag and decorate the cookies. Leave to dry.