Source: Just Eat It
(Adapted from Baking Illustrated)
I would bump the total amount of chips to one and a half cups, but that’s just me. I also used dark brown sugar without any detrimental effects.
1 cup pecans or walnuts (4 ounces)
1 1/2 cups unbleached all-purpose flour (7 1/2 ounces)
1 teaspoon baking powder
1/2 teaspoon table salt
12 tablespoons unsalted butter (1 1/2 sticks), melted and cooled
1 1/2 cups packed light brown sugar (10 1/2 ounces)
2 large eggs, lightly beaten
4 teaspoons vanilla extract
6 ounces white chocolate chips (1 cup) or chopped bar, or 3 ounces each white chocolate and semisweet chocolate chips
Adjust oven rack to middle position; heat oven to 350 degrees. Spread nuts on large rimmed baking sheet and bake until deep golden brown, 10 to 15 minutes. Transfer nuts to cutting board to cool; chop coarsely and set aside. Spray a 13 by 9-inch baking pan with nonstick cooking spray.
Whisk flour, baking powder, and salt together in medium bowl; set aside.
Whisk melted butter and brown sugar together in medium bowl until combined. Add eggs and vanilla and mix well. Using rubber spatula, fold dry ingredients into egg mixture until just combined; do not overmix. Fold in chocolate and nuts and turn batter into prepared pan, smoothing top with rubber spatula.
Bake until top is shiny, cracked, and light golden brown, 22 to 25 minutes; do not overbake. Cool on wire rack to room temperature. Remove bars from pan by lifting foil overhang and transfer to cutting board. Cut into 2-inch squares and serve.