The hands down, undisputed champion of brownie recipes. Deep, rich chocolate, browned butter and toasted walnuts. This will probably be the last brownie recipe you'll ever use (mom will understand). This recipe has been adapted just slightly from the original from Bon Appetit.
Nonstick vegetable oil spray
10 tablespoons (1 1/4 sticks) unsalted butter, cut into 1-inch pieces
1 1/4 cups sugar
3/4 cup natural unsweetened cocoa powder (spooned into cup to measure, then leveled)
1 teaspoon vanilla extract
1/2 teaspoon kosher salt
2 large eggs, chilled
1/3 cup plus 1 tablespoon unbleached all purpose flour
1 cup walnut pieces
Position rack in bottom third of oven; preheat to 325°F. Line 8x8x2-inch metal baking pan with foil, pressing foil firmly against pan sides and leaving 2-inch overhang. Coat foil with nonstick spray. Place walnuts on a sheet pan and place in the oven until just slightly browned and toasted.
Melt butter in medium saucepan over medium heat. Continue cooking until butter stops foaming and browned bits form at bottom of pan, stirring often, about 5 minutes.
Place sugar, cocoa, and salt in a bowl. In a small bowl combine 2 teaspoons water and vanilla.
Remove from heat; immediately add sugar, cocoa, salt mixture and the vanilla and water mixture. Stir to blend. Let cool 5 minutes (mixture will still be hot).
Add eggs to hot mixture 1 at a time, beating vigorously to blend after each addition. When mixture looks thick and shiny, add flour and stir until blended. Beat vigorously 60 strokes.
Stir in nuts. Transfer batter to prepared pan.
Bake brownies until toothpick inserted into center comes out almost clean (with a few moist crumbs attached), about 25 minutes. Cool in pan on rack. Using foil overhang, lift brownies from pan. Cut into 4 strips. Cut each strip crosswise into 4 brownies. DO AHEAD Can be made 2 days ahead. Store airtight at room temperature.