Butter cups Mix brownie batter accorind to package directions. Fill paper-lined or foil-lined muffin cups two-thirds full. Remove wrappers from peanut butter cups; set one in each muffin cup and press down until batter meets the top edge of the candy. Bake at 180ºC or 20 to 25 minutes. Editor's Note: The Test Kitchen staff found Betty Crocker's Fudge Brownie mix bakes best for this recipe.