Combine butter,simple syrup ,peanut butter and heavy whipping cream in medium sauce pan. Heat over medium heat until melted and mixture begins to thicken . remove from heat. Stir in vanilla and allow to cool to room temperature. Once cooled (or if you like it warm) pour or scoop on to ice cream to make your favorite sundae at home. Store any unused sauce in refrigerator and reheat in microwave or on stove.