Clean, wash and cut the rhubarb into small pieces. Boil up the apple juice. Steam rhubarb for about 5 minutes. Stir starch and 3 tbsp. water until smooth. Bind the rhubarb with it, bring to the boil again. Flavour with sugar. Let the groats cool down
Briefly mix 300 ml milk and cream powder in a tall mixing bowl. Whip with the whisk of the hand mixer for approx. 3 minutes until creamy
Stir the sour cream and 1 tablespoon of milk until smooth. Pour the groats into glasses. Spread chocolate cream and sour cream on top. Chill for about 1 hour. Decorate with chocolate shavings, Amarettini and lemon balm