Beat the egg in a bowl with the sugar and the potato starch. Put the milk in a saucepan with the lemon zest, heat it well without boiling, remove the lemon zest, and pour it slowly into the egg and sugar mixture.

Mix well with a whisk while doing this. Return to the heat and bring to a boil, low heat, stirring. Let the cream thicken, it will only take a few minutes then transfer it to a bowl, cover with plastic wrap making it adhere well to the cream so that it does not form a skin. Let it cool completely.

Repeat the procedures of the custard by adding a teaspoon of unsweetened cocoa powder to the egg, sugar and cornstarch. Don’t put lemon zest in milk in this case.

Turn on the oven at 180°C ventilated, 190°C if you have a static oven. Unroll the puff pastry, divide it into three equal parts on the longest side and cut with a knife to obtain three rectangles. Prick with a fork the entire surface of the sheets, this will prevent them from swelling, sprinkle the surface with granulated sugar and bake for about 20 minutes, when the sheet become golden is ready. Let it cool down.

Put the cream in a large bowl, add the vanillin and start whipping with the electric whisk. Start with the slowest speed and then increase. Continue until the cream is very firm. If you need to sweeten the cream, add the icing sugar at the beginning when the cream is still liquid, little by little.

Diplomatic Cream

Diplomatic cream is a basic pastry preparation that involves the combination of custard and sweetened whipped cream.

Put the custard and cocoa custard done before in two different bowls, add the whipped cream, half to each, mix well from bottom to top so you will not ruin the creams.

At this point transfer them into two pastry bags with large star spouts.

Start decorating the first sheet of puff pastry with the white diplomatic cream, make the same number of tufts for each row. Continue with the second sheet using the diplomatic cocoa cream. For the last sheet, alternate a line with white cream and one with cocoa cream. If you only have one spout, first make one cream and then the other, for the double-colored pastry leave an empty line between one and the other in order to subsequently insert the second cream.

Take the pastry with cocoa cream and place it on top of the one with white cream. Lastly, put the two-tone cream sheet. Keep it in the refrigerator untill it’s time to serve the Millefeuille.