How to Make It
Preheat the oven to 350°. Butter an 8-inch square baking pan and line it with parchment paper so the paper extends over two opposite sides.
In a large saucepan, melt the chocolate and butter over low heat, stirring constantly. Remove the saucepan from the heat and stir in the sugar and salt. Let cool slightly, then gradually stir in the beaten eggs. Stir in the vanilla extract. Add the flour and stir until blended. Fold in the chopped walnuts and pour into the prepared baking pan.
Bake the brownies in the center of the oven for 40 minutes, until the tops are glossy and cracked in spots and a toothpick inserted just off center comes out with a few crumbs attached. Let cool completely in the pan, at least 4 hours. Run a knife around the edge of the pan and lift out the brownies using the overhanging parchment paper. Cut the brownies into squares and serve.