HEAT oven to 350ºF.
PREPARE brownie batter as directed on package. Spoon into 20 paper-lined muffin cups.
BEAT cream cheese, sugar, egg, peanut butter and vanilla with mixer until blended. Spoon 1 rounded Tbsp. into center of batter in each cup, pressing down slightly into batter. Bake 30 min. or until centers are set. Cool.
SERVE topped with COOL WHIP and cherries.