Preheat the oven at 175 degrees Celsius.
Butter a cake form and sprinkle evenly some all-purpose flour in the form.
Mix the eggs and the sugar fluffy.
Add the flour, potato flour, vanilla sugar and baking powder and mix well. Pour the mixture in the cake form.
Place in the middle of the oven for 40 minutes. Take the cake bottom out and let it get cold.
Divide the cake in 3 layers.
Whip the cream for the filling together with the vanilla sugar.
Mix the blueberries in the whip cream and stir together.
Place the bottom layer on the serving plate and spread evenly the vanilla cream on it.
Place the second layer of the cake on it and spread evenly the whip cream and blueberry mousse on it.
Place the top layer on the mousse.
Whip the whip cream for the topping and the vanilla sugar to a soft foam. Spread evenly all around the cake, even on the edges.
Time to decorate the cake according to the occasion.