Mix the margarine with the sugar until frothy, gradually stir in the eggs. Also stir in the dark chocolate, nuts and rum. Mix the flour and baking powder and fold into the mixture.
Put in a greased loaf pan and bake at approx. 175 ° C (preheat) for 1 hour with hot air. Let the cake cool down a little and brush with the dark glaze. Tastes best after 1 - 2 days. The cake can be frozen very well.