Parboil the cleaned and washed nettle in boiling water. Drain it, and wash it with cold water again. Preheat a few tablespoons of oil in a pot and fry the chopped onion, garlic and finely chopped carrot.
Optionally, add some sliced mushrooms, if you like. Once softened, stir for 1-2 minutes and add 8 1/3 cups (2 L) water. Let the soup boil until the vegetables soften completely, while stirring the nettle in the pot with a slotted spoon several times throughout.
Finally, season with salt, black pepper and freshly chopped spearmint. Remove the soup from the heat and after 5 minutes, beat the egg and yogurt + a little vinegar. Thicken the soup with this mixture.