In a bowl, mix eggs and sugar. Heat over hot water to 50ºC , beating until doubled in volume. Sift flour and cornstarch together 3 times. Carefully fold the flour, cornstarch and lemon rind into the egg mixture. Pour into greased and floured 23 cm cake pans. Bake at 220ºC until set and springy. Remove from pans and cool on cake racks.
*AMARETTO/CHOCOLATE FILLING*
Heat cream to 80ºC . Stir in chocolate chips and remove from the heat. Stir to melt, then chill overnight. Put half of the genoise on a cake pan and sprinkle with half of the Amaretto. Whip the cream mixture until stiff. Spread quarter of the mixture on the cake. Add top layer of cake and sprinkle with the remaining Amaretto. Ice top and sides of cake with chocolate filling, reserving some it it to pipe through a pastry bag for finishing touches.