Clean the nettle, wash and parboil it for a few min. in boiling water. Drain it and cut it.
Pour 12 1/2 cups (3 L) water in a pot, add the vegetable broth and leave it to come to a boil.
Heat the olive oil and butter in a pan, add both types of onions and braise them briefly. To them add the nettle and after a min. add the flour with paprika.
Stir everything, pour in a ladle of the boiling broth to the nettle, then pour it all into the pot.
Wash the rice with cold water and add it, season with salt and black pepper. Boil everything on medium heat until the rice is ready.
Take the soup off the stove and prepare the thickening agent. Beat the egg with the yoghurt and while stirring nonstop pour a little of the broth to them. Add the thickening agent to the soup, stir and sprinkle with parsley.