1Heat oven to 350°F. Line bottom of 15x10x1-inch pan with parchment paper or spray with cooking spray. In large bowl, stir together bar ingredients until well mixed. Spread in pan.
2Bake 15 to 20 minutes or until golden brown and toothpick inserted in center comes out clean. Cool completely, about 1 hour.
3In large bowl, beat together frosting ingredients with electric mixer on medium speed until smooth. If needed, add more milk to make a spreadable consistency. Spread over cooled bars. Cut into 2x1-inch bars. Garnish with raspberries and mint leaves. Store in refrigerator.