How to Make It
Preheat oven to 350°.
Combine first 4 ingredients in a bowl; stir well. Combine sugar and next 5 ingredients (sugar through egg) in a large bowl; beat at high speed of a mixer for 2 minutes; stir in dry ingredients (dough will be thick). Spoon dough into a 15 x 10-inch jelly-roll pan coated with cooking spray (dough will be spread thin). Bake at 350° for 13 minutes. (Do not overcook.) Let cool completely in pan. Cut into 36 bars. Place bars on wax paper.
Place semisweet chocolate in a heavy-duty zip-top plastic bag; place white chocolate in a heavy-duty zip-top plastic bag. Microwave both bags at MEDIUM-LOW (30% power) for 1 minute or until chocolate is melted. Knead bags until smooth. Snip a tiny hole in corner of each bag; drizzle chocolates over bars. Let bars stand until drizzle hardens.