Combine flour, cinnamon, cloves and baking soda in small bowl. Beat butter and sugars in large mixer bowl until creamy. Beat in pumpkin, egg and vanilla until blended; gradually beat in flour mixture. Stir in 1-1/2 C. white chips and nuts. Spread into greased 15x10 jelly- roll pan. Bake at 350 for 18-22 minutes or until wooden pick inserted in center comes out clean. Cool in pan on wire rack. Place remaining white chips in heavy-duty plastic bag. Microwave on medium- high (70% powder) in bowl for 45 seconds; knead. Microwave at 10 second intervals, kneading until smooth. Cut tiny corner from bag; squeeze to drizzle over bars.