Soak the gelatine in cold water and wash and drain the blueberries in the meantime.
Puree half of the blueberries with 100g powdered sugar and lemon juice. Now dissolve the gelatin dripping wet over low heat and stir into the berry puree.
Now whip the egg yolks with 2 tablespoons of water and the rest of the powdered sugar until frothy, stir into the blueberry mixture and refrigerate.
Whip 1/2 cream until stiff and fold into the blueberry mixture as soon as it starts to thicken.
Put the entire mass in a bowl or mold and chill for 3-4 hours (or overnight) and then dip it in hot water (so that it can dissolve better) and turn it onto a plate.
Now decorate with the remaining blueberries and the cream and serve.