1. Place chicken, celery leaves, onion, salt. ginger, peppercorns and the 2 cups water in a large saucepan; cover. Heat to boiling, then simmer 1 hour or until chicken is tender.
2. Remove from broth; cool while fixing gelatin mixture. Strain broth into a 2-cup measure; add water, if needed, to make 2 cups; return to same saucepan.
3. Soften gelatin in the 1/4 cup cold water in a 1-cup measure; stir into broth. Heat, stirring constantly, just until gelatin dissolves; stir in mayonnaise or salad dressing and soy sauce.
4. Pour into a 6-cup bowl or mold; chill until as thick as unbeaten egg white.
5. While gelatin mixture chills, remove chicken from bones; chop meat very fine. (There should be about 2 1/4 cups.) Stir into chilled gelatin mixture with celery and walnuts. Chill several hours, or until firm.
6. Just before serving, run a sharp-tip, thin-blade knife around top of bowl or mold, then dip bowl very quickly in and out of a pan of hot water. Invert onto serving plate; carefully lift off bowl. Garnish with crisp lettuce and sliced tomatoes, and serve with crusty French bread or toasted hard rolls.