For the punch slices, separate eggs. Beat egg whites with salt until snowy. Beat egg yolks with sugar until pale yellow, sift flour on top, add beaten egg whites and gently fold everything together with a pastry spatula.
Tip onto a baking tray lined with baking paper, spread evenly and bake at 180 degrees for about 8 minutes until light. Turn out the finished sponge cake onto baking paper, remove the baking paper from the base and divide the sponge cake into four pieces.
Keep the two most beautiful pieces, the other two first mix only with 200 g jam, rum and cocoa powder. Add the remaining jam depending on the consistency of the filling, you may not need it.
Spread the mixture on one of the remaining pieces of dough, cover with the other and spread with the punch icing. Let the cake cool and cut into punch slices.