For the Brownies, empty brownie mix into large bowl. Add sour cream, eggs and red food color; mix well. Spoon batter in greased 13x9-inch baking pan.
Bake and cool as directed on package. Cut out cooled brownie with heart-shaped cookie cutters. Place brownies on wire rack set over baking sheet.
For the Icing, mix confectioners’ sugar, water and corn syrup in medium saucepan. Cook on medium-low heat until sugar is melted, stirring occasionally. Stir in vanilla. Tint with desired food color. Spoon or pour icing over top and sides of brownies. (If icing becomes too stiff, gently reheat to pouring consistency.) Let stand until icing is set.
Use remaining icing to decorate or write on brownies, if desired. Pour small amount icing into small resealable plastic bag. Snip off a tiny piece from the corner. Squeeze through hole in bag to decorate or write on brownies. Let stand until icing is set.