1¼cups (about 4½ounces) coarsely chopped pecans or walnuts
2ouncesunsweetened chocolate, coarsely chopped
8tablespoons (1stick) unsalted butter, cut into pieces
2 large eggs
1teaspoonpure vanilla extract
Pinch of salt
4ounces best-quality white chocolate, cut into coarse chunks
Preheat the oven to 350°F. Lightly butter an 8-inch square baking pan; set aside. Place the chopped pecans on a baking sheet and toast, stirring occasionally, until fragrant and lightly colored, about 7 minutes. Set aside to cool slightly.
Meanwhile, place the unsweetened chocolate and butter in a heavy saucepan and melt over low heat, stirring occasionally. Set aside to cool slightly.
In an electric mixer with the whisk attachment, whisk the eggs at medium speed until light and frothy, about 3 minutes. Gradually add the sugar, beating constantly. When all of the sugar has been added, add the vanilla; remove the mixing bowl from the machine.
Meanwhile, sift the flour and salt together onto a sheet of wax paper; set aside.
When the egg-sugar mixture is ready, gently fold in the melted chocolate mixture with a large rubber spatula—don’t incorporate it completely; there should still be a few streaks of chocolate visible. Now gently fold in the flour mixture. When that’s not quite incorporated, fold in the toasted pecans and white chocolate chunks just until everything is well blended, no longer. Transfer the batter to the prepared pan, smoothing it gently to the edges of the pan with a rubber spatula.
Bake for 25 minutes; the top should be dry, but a wooden pick inserted in the center will emerge with some traces of melted chocolate (look for “moist crumbs”). Place the pan on a rack and cool completely. Don’t try to cut the brownies when warm. When cool, cut into 32 bars, each 1 inch wide and 2 inches long.