Drain the cherries and collect the juice. Bring the juice, cherry nectar, vanilla pod, 50 g sugar, lemon juice and salt to the boil and simmer for 5 minutes. Fold in the cherries. Stir the starch with a little water until smooth and thicken the soup, bring to the boil again.
Remove the vanilla pod. Beat the egg white until stiff, add 1 tablespoon of sugar and a few drops of lemon juice. Bring a pot of water to the boil, turn off the stove. Cut off small dumplings with 2 teaspoons, put them into the water and cook in the closed pot for 4-5 minutes in the after-heat.
Arrange the soup warm or cold in plates, add snow dumplings and sprinkle with pistachios.