1Heat oven to 350°F. Spray bottom only of 9-inch square pan with cooking spray. In medium bowl, stir cookie mix, butter and eggs until well blended. Spread in pan.
2Bake 33 to 38 minutes or until toothpick inserted in center comes out clean. Cool completely, about 1 hour.
3Spread with frosting. Sprinkle with walnuts. For bars, cut into 6 rows by 4 rows.