Preparation
Soak the gelatin in cold water.
Grate the zest of lemons and save half for the sponge.
Squeeze out the lemon juice and boil it in a casserole with butter.
Whisk eggs and sugar until light and fluffy.
Keep whisking while you add the lemon mixture. Make sure not to shock the eggs with too much boiling liquid at a time, or they will start to coagulate.
Return the cream to the casserole and heat it up until it starts to thicken while stirring constantly. Do not allow the cream to boil.
Squeeze excess water from the gelatin and dissolve the gelatin in the cream.
Pour the cream in four identical ramekins. It is easier to get the cream out again, if you use a silicone mold, or line the bottom of the ramekin with parchment paper.
Place the Bavarian lemon cream in the fridge to set.

Meanwhile prepare the sponge cake.
Whisk eggs, egg white, sugar and vanilla sugar light and fluffy.
Stir in flour, grated lemon zest and melted butter.
Distribute the batter over a parchment lined baking sheet. The batter layer should be about 50 mm thick.
Bake the sponge in the oven at 160 C /320 F until it starts to turn golden. Should take around 15 minutes.
Place the sponge on a wire rack to cool.
Use a cake ring the same size as the bottom of the ramekin, and make four sponge circles.

Boil black currants with sugar and water to make a thick syrup.

Release the Bavarian lemon cream from the molds.
Roll the cream in finely grated white chocolate.
Place each piece of lemon cream on a sponge disc.
Strain the black currants, discard the berries, and keep the syrup.

Arrange the sponge and Bavarian lemon cream on individual plates, and douse with black currant syrup just before serving.