Follow the sponge cake recipe to make an 8-inch/20 cm sponge cake. Remove it from the baking pan and let it cool completely on a wire rack. Then using a cake slicer, cut the cake into three layers crossways.

To make the vanilla cream, prepare the pastry cream (crème pâtissière in French) first. Use a small sharp knife to split the vanilla bean in half lengthways. Then with the tip of the blade, scrape out the seeds. Bring milk and vanilla seeds to a boil in a small saucepan. In a separate bowl, whisk egg yolks, sugar, all-purpose flour, and corn starch with a hand whisk. Pour the hot milk into the egg mixture while continuing whisking. Bring the mixture back to the saucepan and cook over medium-low heat for a few minutes (constantly whisking) until the cream thickens. Add cold butter, cut into cubes, and mix. Transfer the pastry cream to a shallow dish, cover it with plastic film in contact, and let it cool at room temperature (no need to chill it!).

Pour whipped cream into the bowl of a stand mixer and whip cream. Slowly, one tablespoon at a time, add the pastry cream, and beat until firm.

To assemble the cake, place the first sponge layer on a serving plate, and top with half of the vanilla cream. Then add the second cake layer, spread the remaining cream, and press down gently. Finally, finish the cake with the third sponge layer.

To make the meringue, place egg whites (at room temperature), granulated sugar, and lemon juice in a clean mixer bowl of a stand mixer fitted with a whisk attachment. Or place ingredients in a large bowl and use an electric mixer. Whisk the meringue at medium-high speed (mixer speed) until sugar dissolves and stiff peaks form. Next, cover the entire cake (the top and sides) with the meringue, using a dough scraper, an offset spatula, or the back of a spoon. Next, pick up the meringue on top of the cake to create little peaks.

Torch the top and edges of the cake with a blow torch. Serve right away. If making ahead of time, chill the cake. Cover it with the meringue and torch it just before serving.