In a 12-inch skillet cook chicken in hot oil or shortening, uncovered, over medium heat 10 to 15 minutes or until light brown, turning to brown evenly. Remove chicken, then drain off all but 2 tablespoons fat.
Bias-slice celery. Add celery and onion to skillet. Cook and stir 2 minutes. Carefully add bouillon granules, tarragon, lemon peel, pepper, bay leaf, and 1 cup water. Bring to boiling, scraping up browned bits. Add chicken. Reduce heat, then cover and simmer 35 to 40 minutes or until chicken is tender. Turn chicken once during cooking.
Transfer chicken and vegetables to a warm platter; cover to keep warm. Discard bay leaf. Skim fat from pan juices. Measure and reserve 3/4 cup juices. In the same skillet melt butter or margarine. Stir in flour. Add reserved juices and light cream or milk all at once. Cook and stir until thickened and bubbly, then cook and stir 1 minute more.
In a small mixing bowl beat egg yolks. Gradually stir in thickened cream mixture. Return all to skillet. Cook and stir 1 minute. Stir in parsley and lemon juice. Pour some sauce over chicken; pass remaining. Makes 6 servings.