2 sticks (8 oz) butter
8 oz good-quality semisweet chocolate chips (I used Nestle chips from Costco)
2 cups sugar
1 teaspoon pure vanilla extract
5 large eggs
1/3 cup unsweetened Dutch-process cocoa powder (I used regular cocoa powder)
1/2 tsp salt
2/3 cup all-purpose flour
Preheat oven to 350 degrees F. Line a 13×9 inch metal pan with foil and spray foil with cooking spray. Alternatively, you may use parchment. These are pretty sticky at first! Melt butter and chocolate in a 3-qt heavy saucepan over low heat, stirring, until smooth. Add 1 cup of the sugar to the hot chocolate mixture. Remove from heat and let cool to lukewarm. Whisk in remaining 1 cup sugar and vanilla. Whisk in eggs 1 at a time until mixture is glossy and smooth. Whisk in salt and cocoa powder, then add flour and stir until it disappears (do not overbeat). Spread in pan and bake until a pick inserted in center comes out with crumbs, 25 to 35 minutes (I had to cook mine about 45 minutes). Cool to room temperature then chill for an hour or more. Lift from pan, place on a cutting board, cut into squares.
Makes 1 13×9 inch pan (yield depends on how big you cut your brownies, but they are rich, so small is fine.