Remove the crusts from the toast and cut into small cubes. Halve the vanilla pod lengthwise and scrape out the pulp. Mix the toast bread cubes with egg white, curd cheese, vanilla pulp, 1 teaspoon sweetener and lemon zest to a smooth mixture.
Leave to stand for about 10 minutes. Form dumplings from the curd mixture and let them simmer in boiling salt water for about 10 minutes. In the meantime, wash and clean the strawberries and the Rharbarberries and cut them into large pieces.
Put half of the fruits in a pot, add the remaining sweetener and steam for about 5 minutes. Puree the fruits with a blender. Bring the puree to the boil again and steam the remaining Rharbarber for about 1 minute.
Fold in the remaining strawberries. Season to taste with lemon juice. Arrange the strawberry Rharbarberry groats and quark dumplings on a plate. Sprinkle with pistachios and decorate with mint.