1 tablespoon butter
1 small green pepper, chopped (about 1/2 cup) (optional)
1 small onion, chopped (about 1/4 cup)
1/4 cup chopped celery
1/2 cup barbecue sauce
1 can (12.5 ounces) Swanson® Premium White Chunk Chicken Breast in Water, drained
4 Pepperidge Farm® Farmhouse Premium White Rolls with Sesame Seeds, split and toasted