For the Lemon Curd, beat the egg yolks and 225 g sugar in a large mixing bowl for several minutes until the mixture thickens and pales. Add the lemon juice and pour the mixture into a heavy stainless steel pot with a thick bottom.
Heat the mixture at low heat, stirring constantly with a wooden spoon until it thickens. Do not boil, or the mixture will curdle! Beat in 120 g of butter with a whisk. Stir in lemon zest and 1 pinch of salt.
Heat the mixture until it has pudding consistency. Remove from the heat and pour into a glass with screw cap.
For the vanilla bases, grease 2 cake tins (24 cm Ø) and dust with flour. Preheat the oven (electric cooker: 180 °C/circulating air: 155 °C/gas: level 2). Mix flour, starch, baking powder, sugar and 3⁄4 TL salt in a bowl.
Cut butter into the flour mixture. Grind with your fingertips to produce small crumbs. Add 175 ml milk with the whisks of the mixer and stir for about 2 minutes. Whisk eggs with 60 ml milk and vanilla sugar.
Stir in three portions of 15 seconds each.
Pour the dough evenly into the moulds. Bake in a hot oven for approx. 25 minutes (chopstick test). Let it cool down for about 10 minutes, remove from the mould and let it cool down.
For the Frosting mix egg white, sugar, 85 ml water and maple syrup in a water bath over lightly boiling water. Then whisk with the whisk of the mixer for about 7 minutes. Remove from the water bath and continue beating for a few more minutes until the mixture has cooled down.
Spread a floor with Lemon Curd. Place a second floor on top. Spread the cake generously with the Frosting and enjoy.