- Preheat the oven to 150C/300F. Sprinkle 100 grams of ground hazelnuts on a baking paper. Beat the egg whites until foamy and gradually add powdered sugar and vanilla sugar. Continue to beat until stiff. Fold in 300 grams of ground hazelnuts in two or three additions. Turn the cookie dough on the prepared baking paper and shape the dough with hands into a 3 mm thick rectangle.
- Using a 4 cm diameter round cookie cutter cut out the cookies and place them on a greased lined baking trays. Bake for 20 minutes and remove cookies from the tray to a cooling rack.
- Melt the cocos fat and cool briefly. Combine and sift the powdered sugar and cacao powder into a mixing bowl. Drop in the extract. Slowly stir in melted cocos fat and egg. Coat evenly onto the bottoms of half the cookies with the smooth dark chocolate cream. Flip the remaining cookies on top of the filling and lightly press to form sandwiches.
- Place coarsely chopped chocolate in a bowl and set it over a pot of hot water. Melt the chocolate, stirring until smooth. Spread the tops of the sandwiches with melted white chocolate and decorate each with a roasted hazelnut.