Remove giblets & neck from chicken. Rinse chicken & pat dry. Place chicken in a large cooking bag. Seal bag according to package directions. Cut slits in top of bag. Place chicken & bag in a 13 x 9 x 2 inch baking pan. Bake at 350 degrees for 2 hours or until drumsticks move easily. Remove from bag & let cool. Skin & bone chicken; cut into 1/2 in. pieces. Cover & chill. Combine wine, shallots, tarragon, 1/8 ts salt & 1/8 ts pepper in a small saucepan; cook over medium heat until all liquid is absorbed. Combine herb mixture & yogurt in a medium bowl. Cover & chill several hours. Bring 2 cups water to a boil in a medium saucepan. Add potatoes; cover, reduce heat & simmer 5 min. Or until tender. Remove potatoes from liquid, reserving liquid. Set potatoes aside. Wash beans, trim ends & cut in half. Return reserved liquid to a bowl. Add beans, cover, reduce heat & simmer 5 min. Or until crisp- tender. Drain. Combine reserved potatoes & beans; add oil, 1/8 ts salt & 1/8 ts pepper, tossing gently. Cover & chill. Combine reserved chicken, yogurt mixture & purple onion. Spoon into center of a serving platter. Arrange potatoes & green beans around chicken mixture.