Melt butter in Dutch oven on medium heat. Add celery and yellow onions; cook 5 min. or until softened, stirring occasionally. Stir in flour; cook and stir 2 min. Add chicken broth, peanut butter and Worcestershire sauce; stir. Bring just to boil, stirring frequently; simmer on medium-low heat 10 to 12 min. or until peanut butter is completely melted and mixture is well blended, stirring occasionally.