Soften the gelatin sheets in cold water. Rinse the blueberries and drain well. Set 2 tablespoons aside for garnish. Mix the remaining berries in a saucepan with the sugar, vanilla sugar, and blueberry juice. Bring to a boil. Squeeze the gelatin sheets and add them to the hot berries and dissolve while stirring. Allow to cool.
Once the berry mixture starts to gel, stir in the sour cream. Whip the heavy cream with the sugar until stiff, fold half into the berry mixture. Spoon the berry mixture into cold tin molds and refrigerate for 2 hours. Unmold the blueberry pudding onto a dessert plate and garnish with the remaining whipped cream and the reserved blueberries.