4 ounces unsweetened chocolate
3/4 cup unsalted butter
1 1/4 cups all-purpose flour
1 teaspoon baking powder 
1/4 teaspoon salt
1 3/4 cups granulated sugar
4 eggs
2 teaspoons vanilla extract
1 (3.5 ounce) jar macadamia nuts, coarsely chopped
1 1/2 cups white chocolate chips

Preheat oven to 350 degrees F.

Coat a 13 x 9-inch baking pan with nonstick cooking spray.

Melt chocolate and butter in bowl over simmering water in saucepan. Stir until smooth. Mix together flour, baking powder and salt in small bowl. Stir sugar, eggs and chocolate-butter mixture in bowl. Stir in vanilla extract, then flour mixture until combined. Stir in nuts and half of the chips. Spread evenly in prepared pan. Sprinkle remaining chips over top. Bake for 20 to 25 minutes, until firm and white chips are lightly colored. Cool in pan.