In a small bowl, combine sour cream or yogurt and chutney until well blended; set aside. In a skillet, melt butter or margarine over medium heat. Add onion, bell pepper, celery, and apple. Cook until onion is soft but not browned. Stir in curry powder; cook one minute. Add chicken, and cook for 3 minutes or until heated through. Stir in sour cream mix; cook for 1 minute. Remove skillet from heat, but keep warm. Toast buns. Spoon 1/2 c of mixture onto each bun. Makes 4 sandwiches. Note: I prefer to serve this over hot cooked egg noodles or fettuccine. Recipe By: Food and Fitness Cookbook Per serving: 317 Calories; 8g Fat (24% calories from fat); 27g Protein; 33g Carbohydrate; 67mg Cholesterol; 438mg Sodium