Clean, wash and cut the rhubarb into small pieces. Bring to the boil in a pot with 5 tbsp. water. Cover and simmer for about 5 minutes. Stir sauce powder and 2-3 tbsp. cold water until smooth. Stir into the rhubarb, bring to the boil again briefly.
Season to taste with 1 packet of vanilla sugar and 3-5 tablespoons of sugar. Let the compote cool down.
Mix the double cream, quark, yoghurt, lemon zest, 2-3 tablespoons sugar and 1 sachet vanilla sugar until smooth.
Mix orange juice and liqueur. Place half of the biscuits in a mould (approx. 9 x 20 cm) and sprinkle with half of the orange juice. Spread compote on top. Spread half curd cream on top. Layer the remaining biscuits and sprinkle with the rest of the juice.
Spread the rest of the cream on top. Chill for at least 2 hours. Sprinkle with pistachios.