Start the oven at 175 degrees Celsius.
Whip the egg and sugar white and fluffy.
In a casserole melt the butter and the white chocolate together. Take it away from the heat.
Squeeze the lemon juice from half of the lemon down in the egg mixture.
Add the vanilla sugar, salt and stir together.
Add the melted butter and chocolate, and the flour and stir well.
Place a baking paper in a round baking form. Pour the batter in the form and place in the middle of the oven for 20 minutes.
Take out the cake and let it cool down.
Whip the whip cream lightly soft, add the lemon curd and continue whipping to a hard foam.
Pour in a pastry bag and decorate the cake according to the occasion