PREHEAT oven to 350º F.
COMBINE flour and baking soda in small bowl. Beat peanut butter, butter, SPLENDA® Brown Sugar Blend and SPLENDA® Sugar Blend for Baking in large mixer bowl until creamy. Beat in egg and vanilla extract. Gradually beat in flour mixture. Stir in chunks. Press into ungreased 13 x 9-inch baking pan, distributing chunks evenly.
BAKE for 18 to 20 minutes or until center is set. Cool completely in pan on wire rack. Cut into triangles.