Sift together the flour and baking powder then set aside. In a medium bowl stir chocolate into melted butter until melted and smooth. Mix in the sugar, eggs and vanilla. Gradually blend in the sifted ingredients. Stir in the chocolate chips. Cover dough and chill for at least 2 hours or overnight.
Preheat oven to 180 degrees C. Grease baking trays or line them with baking paper.
Roll the chilled dough into 2cm balls and roll each ball in icing sugar. Place biscuits 5cm apart onto the prepared baking trays.
Bake for 9 to 12 minutes in the preheated oven until the tops are cracked. Remove from baking trays to cool on cake racks.