1. Heat oven to 325°F. Grease 13x9x2-inch baking pan.
2. Beat butter, brown sugar, granulated sugar and peanut butter in large bowl until creamy. Add eggs and vanilla; beat well. Gradually beat in milk. Gradually beat in flour and baking powder, beating thoroughly. Spread about half of batter in prepared pan. Set aside 1/2 cup chocolate pieces; place remaining chocolates evenly on batter, with tips upright. Carefully spread remaining batter over pieces, covering completely.
3. Bake 40 to 45 minutes or until wooden pick inserted in center comes out clean. Cool completely in pan on wire rack.
4. Place reserved 1/2 cup chocolate pieces and shortening in small microwave-safe bowl. Microwave at MEDIUM (50%) 30 seconds or just until melted when stirred. Drizzle over blondies. Before drizzle sets, garnish with additional chocolates, if desired. Cut into bars. Makes 24 to 36 blondies.