Bring broth to a boil. Lower heat and add noodles. simmer for about 8 minutes. meanwhile saute onion in butter, sprinkle with salt and pepper and saute until soft. stir in mint and parsley. cook for 1 minute, then stir into the noodles. in bowl, stir yogurt until smooth. add eggs and mix well. stir in 1/2 cup of soup, a spoonful at a time. pour this back into the soup, heat to a simmer and serve