Bring water, salt, and chicken parts to boil in large saucepan; cover. Simmer 1 hour.
Add celery, leek, carrot, and potatoes; simmer 20 minutes.
Remove chicken; cube meat; return to soup. Add peas; simmer about 8 minutes. Remove grease from surface of soup. Lightly beat egg yolks; stir into yogurt. Remove soup from heat; stir in yogurt mixture; adjust seasoning. Garnish with lettuce; serve at once.
Please note that some ingredients and brands may not be available in every store.