Separate the eggs and beat the egg whites until stiff. Beat the egg yolks with sugar until frothy. Add the softened butter and mix well.
Briefly bring the ground poppy seeds to the boil with the milk and sugar and add the ground rusks, walnuts and the juice of the lemon with the peel. Add the poppy seed mixture to the egg mixture and stir well. Fold in the egg whites.
Pour into a slightly higher baking sheet lined with backpacker and bake at 180 ° C or gas mark 3 for about 30 minutes.
For the glaze, melt the chocolate with the rest of the ingredients over low heat and spread on the cake while it is still warm.