Peanut butter bars

Instructions

1. Preheat oven to 350ºF. Line a 9- X 13-inch baking pan with aluminum foil; coat foil with cooking spray.
2. Whisk together all-purpose flour, whole wheat flour, baking powder, baking soda and salt in a bowl. Whisk in oats and set aside.
3. With an electric mixer on medium-high speed, beat peanut butter, brown sugar, granulated sugar and butter in a large bowl until well blended. Add eggs, one at a time, beating well after each addition; beat in vanilla.
4. At low speed, add one half of flour mixture to peanut butter mixture, then one half of milk, beating just until incorporated. Repeat with remaining flour mixture and milk, beating until well mixed. Spread batter in prepared pan. Bake until golden at edges and a toothpick inserted in center comes out clean, about 30 minutes. Transfer to a rack.
5. Meanwhile, to make icing, combine peanut butter and butter in a medium microwavable bowl. Microwave on high until butter is melted, about 30 seconds; whisk until smooth. Add powdered sugar and milk; whisk until smooth. Immediately spread icing evenly over hot cake. Cool completely. Cut into 24 bars. Yields 1 bar per serving.