Dissolve the marzipan in the water. Add ¾ of the sugar, egg yolk, salt, lemon zest and stir well. Beat the egg whites with the remaining sugar until stiff, fold in. Sieve the flour, starch and baking powder and fold them into the mixture as well.
Spread the mixture on a baking tray lined with baking paper. Bake on the middle rack for about 10 minutes, turn out and allow to cool. Peel off the paper.
Cut the dough sheet into 3 equal rectangles. Spread a jam on each of the strips and place them on top of each other.
Knead the marzipan with the powdered sugar. On a surface dusted with powdered sugar, roll out to the size of the top sponge cake plate, place on top and press down. Wrap the stack in foil, pack it between two boards, weigh it down and let it stand for 24 hours.
Then cut the biscuit into small cubes. Spread smoothly stirred apricot jam on the marzipan and let it dry. Melt the fondant or cake icing slowly in a water bath. Let cool, reheat and add the rum.
Place the biscuit cubes on a fork, dip in the glaze, drain. Carefully place the petits fours on a wire rack and allow to dry.
Finally, decorate the petits fours with pieces of cherries, pistachios and walnuts. cut off and decorate petits fours. Finally put them in small paper cases.