Heads are cleaned and washed, then pour 6 cups cold water, add salt and cook on medium heat. Meat, brain and tongue are cut into small pieces and return to soup. Add spinach, chopped. In fat sauté finely chopped onion, red pepper and flour, dilute with a little broth and pour in the soup. Soup boil for another 10-15 minutes, thicken with the egg and yogurt and serve sprinkled with pepper.