Lightly grease 4 baking trays. Sprinkle with anise seeds. Set aside until needed.
Mix the flour and baking powder together in a bowl until well blended. Place the eggs, sugar and vanilla in a large bowl; beat until light and frothy, 5 to 8 minutes. Slowly stir in the flour mixture until a thick dough forms.
Working with handfuls of dough, roll out the dough onto a lightly floured surface until 5mm thick. Lightly sift icing sugar over the dough. Place springerle moulds onto the dough; press down hard and evenly until the mould's design registers in the dough. Remove the mould. Use a small knife to cut around each biscuit and place on prepared baking trays. Repeat, until all dough has been used. Cover the biscuits with a lightweight cotton cloth and allow to dry 8 hours, or overnight.
Preheat oven to 120 degrees C.
Bake biscuits in preheated oven until tops are pale brown and set, 25 to 30 minutes. Cool on a rack. Store in an airtight container.