PREHEAT oven to 350º F. Grease 8- or 9-inch-square baking pan.
COMBINE flour, baking powder and salt in small mixing bowl. Beat butter, brown sugar and vanilla extract in large mixer bowl until creamy. Beat in egg. Gradually beat in flour mixture. Stir in broken baking bars. Press into prepared baking pan.
BAKE for 20 to 25 minutes or until golden brown. Cool completely in pan on wire rack. Cut into bars.