Knead all ingredients together into a smooth dough. Add a few drops of cold water, if it is too dry. Allow the dough to rest for at least an hour. Roll out on a flour-dusted countertop. Cut out small rectangles or use a cutter. Place them on a baking tray lined with baking paper. Preheat the oven to 180°C (350°F/Gas 4). Bake until done in approx. 10 minutes. Leave them to cool before serving, allowing the chocolate to set.