4 ounces bittersweet chocolate
1 1/2 cups all-purpose flour
1/2 teaspoon baking powder
1/8 teaspoon salt
10 tablespoons unsalted butter
3/4 cup granulated sugar
3 large eggs
2 1/2 teaspoons vanilla extract
3/4 cup coarsely chopped macadamia nuts, optional
- Preheat oven to 325 degrees F. Line a 9-inch square baking pan with foil and lightly spray with nonstick cooking spray.
- Chop 6 ounces of the white chocolate very fine and set aside. Chop remaining 6 ounces white chocolate and bittersweet chocolate coarsely; set aside.
- Sift the flour, baking powder and salt together in a small bowl; set aside.
- Melt the butter in a small saucepan over low heat; do not allow to bubble. Remove pan from heat and add the finely chopped white chocolate but do not stir. Set aside.
- Using an electric mixer on medium-high speed, beat the sugar, eggs and vanilla in a medium-sized bowl until thick and pale, about 5 minutes.
- With the mixer on low speed, add the butter mixture and mix to combine, about 115 to 20 seconds. Scrape down sides of the bowl.
- Add the flour mixture on low speed and mix just until combined. Fold in white chocolate and bittersweet chocolate (and macadamia nuts, if using) with a rubber spatula. Spread batter evenly into prepared pan. Bake until toothpick inserted near the center comes out with a few moist crumbs, about 30 to 35 minutes.
- Let cool completely before cutting into squares.