Tarragon Chicken Salad Sandwiches

The only other chicken salad sandwich recipe that I have had that is better than this was made by a man I knew growing up, who as far as I know still won't share his recipe. Sigh....
Tarragon Chicken Salad Sandwiches

From: Treasury of Cooking Healthy

1 1/4 lbs. boneless skinless chicken breasts, cooked
1 cup thinly sliced celery
1 cup seedless red or green grapes, cut into halves
1/2 cup raisins
1/2 cup plain nonfat yogurt
1/4 cup mayonnaise
2 Tbs. shallots or onion, finely chopped
2 Tbs. fresh tarragon, minced or 1 tsp. dried tarragon
1/2 tsp. salt
1/8 tsp. white pepper
6 lettuce leaves, washed
6 whole wheat buns, split

Cut chicken into scant 1/2" pieces. Combine chicken, celery, grapes and raisins in a large bowl. Combine yogurt, mayo, shallots, tarragon, salt and pepper in a small bowl. Spoon over chicken mixture; mix lightly.

Place 1 lettuce leaf in each bun. Divide chicken mixture evenly; spoon into buns.