Saute onion, mushrooms and celery in olive oil until tender, about 5 minutes. Add dry sherry. Saute for 1 minute. Remove from heat. Cover and chill. Add chicken, cheese, olives and tarragon. Adjust seasoning with salt and pepper.

For each sandwich: Brush one phyllo sheet with melted butter. Cover with second sheet. Brush with butter. Repeat with a third sheet. Spread 1 cup of filling along a line one inch from bottom edge and both sides of the top phyllo sheet. Fold bottom over filling and then both side edges. Roll jelly-roll fashion into a tight cylinder. Brush with butter. Place on a sheet pan sprayed with non-stick spray. Bake at 400 degrees F until golden brown, about 20 minutes. Let cool for 15 minutes before serving whole or bias-sliced in half.

Recipe and Photo Courtesy of The California Olive Industry.