Let the puff pastry sheets thaw at room temperature for about 15 minutes. Then cut into 4 strips (each strip approx. 12x5.5 cm). Put 50 g sugar in a deep plate, press one side of the puff pastry strips lightly into the sugar. Place the unsweetened side on a baking tray lined with baking paper and bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 20 minutes. Remove from the oven, place on a rack and allow to cool. Then cut open with a sharp knife.
Clean, wash and cut the rhubarb into pieces. Bring rhubarb, apple juice, lemon juice and 75 g sugar to the boil in a small pot. Cover and simmer for about 4 minutes. Then take it off the stove and let it cool down. In the meantime soak the gelatine in cold water. Mix yoghurt, quark, vanillin sugar, grenadine syrup and 50 g sugar. Whip the cream until stiff. Stir the rhubarb into the quark mixture. Melt the squeezed out gelatine in a small pot at low heat. Remove from the stove. Stir 4 tablespoons of the rhubarb quark mixture drop by drop into the melted gelatine. Then let it run into the rhubarb-quark mixture while stirring.
Whip the cream until stiff. Stir the rhubarb into the quark mixture. Melt the squeezed out gelatine in a small pot at low heat. Remove from the stove. Stir 4 tablespoons of the rhubarb quark mixture drop by drop into the melted gelatine. Then let it run into the rhubarb-quark mixture while stirring. Place the mixture in a cool place for 6-9 minutes until the mixture begins to gel. Fold in the cream in portions. Refrigerate for another 4-6 minutes. Pour cream with a tablespoon onto the lower puff pastry plates, place lid on top. Refrigerate for about 1 1/2 hours. Sprinkle with pink sugar and serve decorated with lemon balm
Place the mixture in a cool place for 6-9 minutes until the mixture begins to gel. Fold in the cream in portions. Refrigerate for another 4-6 minutes. Pour cream with a tablespoon onto the lower puff pastry plates, place lid on top. Refrigerate for about 1 1/2 hours. Sprinkle with pink sugar and serve decorated with lemon balm