Best cocoa brownie
Makes 16 large or 25 small brownies
10 tablespoons (1 1/4 sticks) unsalted butter, cut into pieces
1 1/4 cups sugar
3/4 cup plus 2 tablespoons unsweetened cocoa powder
1/4 teaspoon salt
1/2 teaspoon pure vanilla extract
2 cold large eggs
1/2 cup all-purpose flour
2/3 cup walnut or pecan pieces
Position rack in the lower third of the oven and preheat the oven to 325 degrees (note lower temperature than in previous recipes).
Line the bottom and sides of an 8-inch-square baking pan with foil, leaving an overhang on two opposite sides.
Combine the butter, sugar, cocoa and salt in a medium heatproof bowl, then set the bowl in a wide skillet of barely simmering water. Stir from time to time until the butter is melted and the mixture is smooth and hot enough that you want to remove your finger fairly quickly after dipping it in to test (150 degrees on an instant-read thermometer). Remove the bowl from the skillet. In this recipe, cool the mixture briefly until it is only warm, not hot.
Stir in the vanilla with a wooden spoon. Add the eggs one at a time, stirring vigorously after each one. When the batter looks thick, shiny and well blended, add the flour and stir until you cannot see it any longer, then beat vigorously for 40 strokes with a wooden spoon or a rubber spatula. Stir in the nuts. Spread evenly in the lined pan. Bake until a toothpick plunged into the center emerges slightly moist with batter, 20 to 25 minutes. Remove from oven and let cool completely on a rack.
