Mix the eggs and sugar with the mixer, then add the butter, the sifted flour with the baking powder and the rum. Just stir in the nuts and chocolate shavings with the spatula.
Line a loaf pan with baking paper, pour in the dough and bake for about 1 hour at 160 degrees (convection oven).
After cooling, melt the chocolate in a water bath and brush the cake with it.