Mix the sugar, the buckwheat flour, the potato starch, the vanilla yeast, the cinnamon, and a pinch of salt.
Beat the eggs until foamy.
Mix the flour mixture into the eggs until evenly mixed.
Pour the dough into a 7" buttered round cake pan.
Cook for 30 minutes in a 400 degree oven.
Let it cool. Take it out of the pan, and slice it into 2 discs.
Spread the bottom one with blueberry jam and put the other disc on top.
Whip the heavy cream with the powdered sugar.
Spread the whipped cream on top and complete it with wild berries. Serve and enjoy!