Whisk the egg yolks with the remaining eggs, sugar, salt and lemon zest on a hot water bath with the whisk of the hand mixer. Remove from water bath and beat cold. Mix flour and starch, sieve onto the egg mixture and fold in. Melt the fat and fold in. Remove approx. 1/3 of the mixture and fold in cocoa.
Grease a box form (30 cm long; 2 litres capacity) and line with breadcrumbs. Pour in the remaining light-coloured mass. Pour the dark mass on top, pull through with a spoon handle and bake in a preheated oven (electric range: 175 °C/ gas: level 2) for 50-60 minutes. As soon as the mixture begins to brown (approx. after 15 minutes) cut in with a knife. After baking, leave to cool in the mould for approx. 15 minutes. Then carefully turn out and dust with icing sugar. Whip the cream until semi-stiff, allow the vanillin sugar to trickle in and fold in the orange liqueur. Cut the cake into slices and arrange on plates.
After baking, leave to cool in the mould for approx. 15 minutes. Then carefully turn out and dust with icing sugar. Whip the cream until semi-stiff, allow the vanillin sugar to trickle in and fold in the orange liqueur. Cut the cake into slices and arrange on plates. Add a dash of orange liqueur cream and decorate with lemon balm. Makes about 16 pieces