-
Preheat oven to 325°. Grease a 9-inch square baking pan.
-
Line bottom of pan with parchment paper; set aside.
-
Chop 1/2 the white chocolate into very small pieces.
-
Chop remaining white chocolate and bittersweet chocolate into large chunks; set aside.
-
Sift flour, baking powder and salt.
-
Melt butter in a small saucepan--don't allow to bubble or color. Remove from heat and add finely chopped white chocolate. DON'T STIR, just set aside.
-
With mixer, beat sugar, eggs and vanilla until thick and lemon colored, about 5 minutes.
-
Lower speed and add the butter mixture; mix just to blend.
-
Add flour mixture and mix just until combined. Use rubber spatula to fold in chocolates and nuts.
-
Scrape the batter into the prepared pan.
-
Bake brownies until set, approx 30 minutes, until a toothpick in center clings moist crumbs. Just don't over bake.
-
Let cool about a 1 hour, then cut into squares.