HEAT oven to 350 degrees F.
STIR brownie mix, melted shortening and egg in medium mixing bowl until evenly moistened. Scoop into 1 1/2-inch balls or drop by rounded tablespoons onto ungreased cookie sheet.
BAKE 10 to 11 minutes or just until set. Cool on cookie sheet 1 minute. Transfer to cooling rack. Spread frosting on cooled cookies. Sprinkle with chopped peanuts.