Wash, sort and drain the blueberries. Soak gelatine in cold water. Cream sour cream, vanilla sugar and 70 g sugar with the whisk of the hand mixer for about 5 minutes. Add buttermilk. Squeeze out the gelatine, dissolve, mix with 3 tablespoons of the cream and stir into the remaining cream.
Chill the cream for about 15 minutes. Place the muesli bars next to each other and put a cake frame around them or fold a border of extra-strong aluminium foil and put it around it. Whip the cream until stiff. Stir the cream again and fold in the cream. Pour 1/3 of the cream onto the bars and sprinkle some blueberries on top. Put 2 tablespoons of blueberries aside for decoration. Layer again in the same way and finish with a layer of cream. Chill the cake for at least 3 hours. Caramelise 2 tablespoons of sugar. Stir in 1 teaspoon butter well and then mix with the oat flakes.
Layer again in the same way and finish with a layer of cream. Chill the cake for at least 3 hours. Caramelise 2 tablespoons of sugar. Stir in 1 teaspoon butter well and then mix with the oat flakes. Put the caramel on a piece of baking paper and let it cool down. Coarsely chop the caramel. Cut the cake into 10 pieces and decorate with blueberries and caramel