Preheat the oven to 325°F.
Cut slightly the cardamom pods, use one or two according to your taste.
Heat the milk just a little, add the vanilla extract and the cardamom pods, set aside.
Line with parchment paper a 6 inch springform pan by placing a disk of paper on the bottom and a strip of paper to cover the sides exceeding a couple of inches the height of the pan.
Place in a bowl the eggs and sugar and beat with a whisk for 5 minutes to obtain a soft and airy mixture.
Remove the cardamom pods from the milk and add it to the whipped eggs.
Sieve flour and baking powder and add them little by little to the bowl containing eggs, sugar and milk. Stir gently with a spatula from the bottom upwards to obtain a light batter without any lump.
Pour the batter into the springform pan, bake for 45 to 50 minutes. The cake is done when a toothpick inserted into the centre comes out dry.
While the sponge cake is baking, let's prepare the yoghurt icing: put in a bowl the cream, greek yogurt and sugar, whip using a whisk until the mixture gets thick. Put the icing in the fridge until ready to use.
Once the sponge cake is done remove it from the pan and let cool completely on a wire rack.
When the cake is cool, cut it horizontally to get three discs of equal height.
Place the base disk on a cake serving plate, cover the surface of the disk with yoghurt icing and two generous tablespoons of blueberry jam.
Repeat the previous step for the middle sponge cake disk.
Lay finally on the second disk you've stuffed with joghurt icing and jam the last sponge cake disk, with the cut part facing inside the cake.
Cover the outside of the cake with the remaining yoghurt icing and decorate with fresh blueberries.
If you don't serve the cake immediately, store it in the fridge until ready to taste.