Add the lemon juice with water to 1 liter. Mix the cornstarch, 75 g sugar and 4 tablespoons of the lemon water. Heat the rest of the lemon water with a little lemon zest. Take the pot off the hob. Slowly stir the mixed cornstarch into the boiling lemon water and bring to the boil again. Season the soup with sugar and peel off with whisked egg yolks.
Beat the egg white until stiff and sweeten it with the sugar. Cut small dumplings from the egg snow and place on the hot, but not boiling, soup. Close the pot with a lid and allow the dumplings to set in about 5 minutes.
Tip: If the soup is to be served cold, only take 30 g cornstarch and let the dumplings set in hot water.