How to make
Mix the all of the strained yogurt and sour cream. Add the sugar and mix.
Place the first cake layer and spread the mixture and half of the blueberry jam on top.
Place the second sponge cake layer and spread only with the mixture.
Place the third sponge cake layer and spread with the mixture and the other half of the blueberry jam.
Place the fourth sponge cake layer and spread the mixture on it, as well as the sides of the cream cake.
Grind the walnuts and sprinkle them over the cake.
Leave the French Rustic Cake in the fridge for 1 day.