Beat the eggs, sugar and margarine until frothy. Carefully fold in the flour and baking powder. Then stir in the egg liqueur and the chocolate shavings. Line a muffin baking sheet with molds and fill 2/3 with the batter. Bake at 200 degrees or 180 degrees (with convection) for about 15-20 minutes. Melt the couverture separately. Cover the muffins with a dark coat, let them dry a little and decorate with white couverture.