unsweetened chocolate , finely chopped • cocoa Dutch - process powder (3/4 oz) • water hot • sugar (12¼ oz) • all-purpose flour (8¾ oz) • baking soda • salt • buttermilk , at room temperature • vanilla extract • eggs egg yolks large 2 large plus , at room temperature • unsalted butter , cut into pieces , at room temperature (1½ sticks) 12 • sugar •
