For the Archduke Johann cake, first prepare the dough. To do this, melt the cooking chocolate or couverture (preferably in a water bath). Beat the egg whites with the remaining sugar until stiff.Cream the butter with a little more than half of the sugar. Stir in melted chocolate and yolks. Fold in beaten egg whites and breadcrumbs alternately.
Grease a cake pan with melted butter and sprinkle with flour. Pour in the mixture and bake in a hot oven at 180°C for about 40-50 minutes. Lift out and let cool briefly.
Prepare the cream for the Archduke Johann cake. Melt the chocolate. Cream the butter with the powdered sugar, stir in the melted chocolate and the egg and mix everything well until fluffy. Cut the cake once crosswise, spread with jam and put some cream. Sprinkle with chopped pumpkin seeds. Reassemble and spread again all around first with jam, then with cream. Sprinkle the Archduke Johann cake with pumpkin seeds.