Lightly spray 11x17 inch cookie sheet with vegetable pan spray.
In medium bowl, combine flour and baking powder;set aside. Place white chocolate and butter in microwave-safe bowl. Microwave at 50% 1-2 minutes, stirring every 30 seconds, until chocolate is melted. Remove from microwave; cool slightly.
In large bowl, beat eggs, granulated sugar, brown sugar and vanilla with electric mixer until well blended. Gradually beat in white chocolate mixture. Add flour mixture; mix well. Stir in cashews. Spread mixture evenly into prepared pan. Sprinkle chocolate chips evenly over top.
Bake 25-30 minutes or until golden brown. (Surface of brownie will crack during baking.) Place pan on cooling rack to cool completely.
Makes 24 brownies.
(Recipezaar won't let me put the amount of butter- it's 3/4 cup).