Tarta San Marcos

Recipe: Sponge cake: 400g eggs 200g sugar 200g flour Egg yolk: 200g eggs 200g sugar A few drops of lemon juice Truffle filling: 700g cream 200g chocolate Cream: 400g cream 1 tablespoon icing sugar Syrup: 150g water 1 tablespoon sugar Orange peel Liqueur to taste