In medium bowl, mix Bisquick mix, sugar and cocoa. Cut in butter, using pastry blender (or pulling 2 table knives through ingredients in opposite directions), until mixture is crumbly. Press half of the crumbly mixture (2 cups) on bottom of ungreased 13x9-inch pan. Sprinkle with white vanilla baking chips. Spoon chocolate mixture over crumbly mixture and chips; spread evenly. Sprinkle with remaining crumbly mixture and 1 cup chocolate chips. Press lightly with fork.