Heat oven to 350 F.
Grease 8- or 9-inch baking pan.
Beat peanut butter, butter, brown sugar and granulated sugar in large bowl until well blended.
Add egg, milk and vanilla; beat well.
Stir together flour, baking soda and salt; add to peanut butter mixture, beating until well blended.
Spread one half of batter in prepared pan.
Sprinkle baking pieces over batter.
Drop remaining batter by 1/2 teaspoonfuls over mixture, covering baking pieces.
Bake 25 to 30 minutes or until lightly browned.
Cool completely in pan on wire rack.
Cut into bars.