Prepare and bake brownies in 13x9 in. baking pan according to package directions. Cool completely. Preheat oven to 250 degrees. Line baking sheet with parchment paper; set aside. Beat egg white in lg. bowl until foamy. Add almond extract, if desired; beat until soft peaks form. Gradually add sugar; beat until stiff peaks form. Fill pastry bag with egg white mixture. Pipe 24 skull and cross bones shapes onto prepared baking sheet. Bake about 12 min. or until very lightly browned and set. Cool on pan on wire rack. Carefully remove meringues from parchment paper.Decorate with red gel for eyes and black gel for mouths. Frost brownies and cut into 24 rectangles. Place one meringue on each brownie.