Adapted from Alice Medrich's Bittersweet
10 tablespoons butter
1 1/4 cups sugar
3/4 cup plus 2 tablespoons cocoa powder
1/4 teaspoon salt
1 teaspoon vanilla
2 large eggs, cold
1/2 cup flour
2/3 cups nuts of your choice, chopped, optional
Preheat oven to 325º. Line the bottom and sides of an 8 x 8 inch square pan with foil or parchment, leaving some overhang for easy removal.
Combine butter, sugar, cocoa and salt in a medium microwavable bowl. Gently heat, stirring at 30 second increments, till butter is melted, mixture is smooth and hot to the touch. There will be a bit of a gritty look to the batter, but don't worry.
Stir in vanilla. Add eggs one at a time, stirring vigorously after each addition. Add flour and mix till well incorporated. Add nuts if using. Spread evenly in prepared pan.
Bake till toothpick inserted into the center comes out with slightly moist crumbs, about 20 to 30 minutes depending on your oven. Cool completely on rack. Remove using the parchment or foil liner to cut and serve.