For the oat cookies, knead the butter, sugar, eggs, oats, flour, baking powder and grated chocolate into a smooth shortcrust pastry. Using a teaspoon, place small mounds on a prepared baking sheet.
Bake in a preheated oven at 200 °C for 15 minutes. Then leave to cool on a cooling rack. Chop the chocolate coating and melt in a bain-marie.
Coat one side of each cookie with the chocolate coating.