Insert metal accessory rack.
Preheat oven to 350°F.
Grease a 9 inch square baking pan.
In food processor, place chocolate chips and sugar.
Process until chocolate is as fine as sugar.
Add butter, eggs and vanilla and mix for 1 minute.
Blend in flour, baking powder, salt and white chocolate.
Place batter in prepared pan.
Bake for 40 to 50 minutes until toothpick inserted in center comes out clean.