PREHEAT oven to 350° F.
BEAT brown sugar, peanut butter, butter and granulated sugar in large mixer bowl until creamy. Beat in egg and vanilla extract. Gradually beat in flour and baking soda. Stir in Nestlé Hearts.
PRESS dough into 9-inch-square baking pan, distributing Nestlé Hearts evenly.
BAKE for 25 minutes or until golden and wooden pick inserted near center comes out clean. Cool completely in pan on wire rack. Cut into bars.