Lightly grease baking trays with butter and preheat oven to 170°C.
Beat butter, sugar and essence with an electric mixer until creamy. Sift in flour and baking powder. Add milk powder and ground almonds to mix.
Place dough in between two plastic sheets and roll out to 0.4cm thickness. Cut into 4cm rounds with a fluted ring cutter. Lightly brush the rings with beaten egg white. Sprinkle sparingly with almond nibs.
Bake cookies for 15-16 minutes or until golden. Leave the cookies to cool completely on a wire rack before storing in airtight containers.