Coarsely chop the chocolate, coconut oil and crispy puffed rice and melt in a bowl over a warm water bath. Place baking paper on a tray (must fit in the refrigerator) and place the baking frame (approx. 25 x 35 cm) on top. Pour the puffed rice mixture into the baking frame, smooth it down evenly with the pallet and put it in a cool place
Soak gelatine in cold water. Clean, wash and cut the rhubarb into pieces. Mix 3 tbsp. cherry nectar with groats powder. Put the rest of the cherry nectar, 1 1/2 tbsp. sugar and rhubarb in a pot and boil for about 1 minute. Pour rhubarb through a sieve, collect the juice and bring to the boil again. Stir in mixed groats powder and boil for about 1 minute. Add the rhubarb again. Pour the compote into a large, flat container and let it cool
Mix yoghurt, 100 g sugar, and lemon juice in a large bowl. Squeeze the gelatine and dissolve. Stir in 4 tablespoons of cream, stir into the rest of the cream. Chill the cream until it starts to gel (approx. 10 minutes). In the meantime, whip the cream until stiff and allow vanilla sugar to trickle in. Fold cream into the cream. Pour the cream onto the chocolate base, pour the rhubarb compote in patches with a teaspoon onto the cream and marble with the teaspoon. Chill the cake for at least 4 hours. Cut the cake into approx. 35 pieces (approx. 5 x 5 cm)