Preheat oven to 180°C (160°C fan-forced) and line 2 baking trays with baking paper.
Using an electric stand mixer beat the butter and sugar together until pale and fluffy. Add the flours, cocoa and melted chocolate, beating slowly until combined.
Divide dough into two equal pieces. Place each piece of dough between two sheets of baking paper and roll to a thickness of 5mm. Chill in the refrigerator for 30 minutes.
Using a 6.5cm biscuit cutter, cut out 40 biscuits and place on prepared baking trays. Bake in preheated oven for 12 minutes or until golden. Remove from oven and place on a wire rack to cool.
Using a spatula, evenly spread melted chocolate over the top side of each cooled biscuit. Place hundreds and thousands in a small bowl and dip each biscuit to coat. Place biscuits back on wire racks to allow chocolate to set.