MAKE THE PAN DI SPAGNA

Cup of Yum
1. Beat the eggs with the sugar with an electric whisk for about 15-20 minutes. The mixture should be well frothy and triple its volume.
2. When the mixture is foamy, creamy and well combined, add the sifted flour a little at a time. Mix with a spatula using a rotating motion from the bottom to the top.
3. Pour the dough into a rectangular cake pan about 22x16 cm (9x7 inch) lined with parchment paper or greased with butter. Bake in a preheated oven at 170°C (338°F) for about 40 minutes. Remove from oven and allow to cool.

MAKE THE DIPLOMAT CREAM

1. While the Italian sponge cake is baking, prepare the diplomat cream. In a small saucepan, heat the milk with the lemon zest, taking care not to boil. In another saucepan, quickly mix the egg yolks with the granulated sugar.
2. When the two ingredients are well mixed and just frothy, add the flour. Continue stirring until all the flour is incorporated. Finally, add the hot milk.
3. Turn on the heat and cook the cream for about 10 minutes, while stirring, until it starts to bubble and thicken. Turn off the heat and pour the cream into a cold container and let it cool completely with a plastic wrap in contact.
4. Mix the heavy cream with the powdered sugar. Whip the sweetened cream. Add it to the cooled pastry cream. The diplomat cream is ready!

BAKING THE PUFF PASTRY

1. Roll out the puff pastry on a sheet of baking paper and make two equal rectangles the size of the sponge cake. Prick the entire surface with the prongs of a fork to prevent the pastry from puffing up during baking.
2. Sprinkle generously with granulated sugar. Bake in a preheated oven at 180°C (350°F). This will take about 15 minutes. Remove from the oven when both puff pastry sheets are well browned and caramelized. Allow to cool.

MAKE THE DIPLOMAT CAKE

1. Place a sheet of cooked puff pastry on a serving dish. Spread it with about half of the Diplomatic Cream. Level it well with a spatula.
2. Take the sponge cake and remove the dark part from the edges and the surface. Cut it with a sharp knife and place it on top of the diplomat cream.
3. Sprinkle the entire surface of the pan di spagna with the Alchermes liqueur. Moisten the cake very well and generously all over the surface and also on the edge. NOTE: I used pure Alchermes, as per Italian tradition. If you prefer a less alcoholic taste, you can dilute it with water. Read the parparagraph for the best substitutes.
4. Cover the pan di spagna with the rest of the diplomat cream. Spread it well.
5. Close the top of the diplomatic cake with the second sheet of puff pastry.
6. Sprinkle with plenty of powdered sugar. Allow the cake to rest in the refrigerator for at least 2 hours before serving.