Put the chicken legs to boil on low heat. Take them out to cool and strain the broth into another pot. While they're cooling, chop the potatoes, carrot, peppers and onion finely. Add them to the broth and boil 20 min.
Season the chicken legs, strip the meat from the bones and add it to the soup. Add the vermicelli, season with black pepper, salt, parsley and boil until the vermicelli is ready.
In a bowl mix the yoghurt, egg yolk and flour. Pour a few ladles of the soup over them while stirring nonstop. Pour it back into the main soup while stirring nonstop and once it comes to a boil again, remove from the heat and serve.