-
1
Position a rack in the lower third of the oven and preheat the oven to 325u00b0F Line the bottom and sides of an 8x8-inch square baking pan with parchment paper or foil, leaving an overhang on two opposite sides.
-
2
Spray the pan and lining with cooking spray.
-
3
Combine the butter, sugar, cocoa, and salt in a medium heatproof bowl and set the bowl in a wide skillet of barely simmering water.
-
4
Stir occasionally until the butter is melted and the mixture is smooth, though it will appear somewhat gritty.
-
5
Remove the bowl from the skillet and set aside briefly until the mixture is only warm, not at all hot.
-
6
Stir in the vanilla with a wooden spoon.
-
7
Add the eggs one at a time, stirring well after each one.
-
8
When the batter looks thick, shiny, and well-blended, add the flour and stir until all the streaks of flour disappear, then beat vigorously for 40 more strokes with the wooden spoon or a rubber spatula.
-
9
Stir in the nuts, if using. Spread evenly in the prepared pan.
-
10
Bake until a toothpick plunged into the center emerges slightly moist with batter, about 25 minutes.
-
11
Let cool completely on a wire rack.
-
12
Set the pan in the freezer for 10 minutes (it will make for clean cutting of the brownies).
-
13
Lift up the ends of the parchment or foil liner, and transfer the brownies to a cutting board.
-
14
Cut into 16 squares.
