Preheat oven to 350. Line a 9 inch square metal cake pan with foil, draping the foil over the edges. Lightly butter the foil. In large pan, melt butter with the unsweetened chocolate over very low heat, stirring occasionally. Remove from heat. Whisking them in one at a time, until thoroughly incorporated, add the unsweetened cocoa, sugar, eggs, vanilla extract and flour. Pour the batter into the prepared cake pan and smooth the surface. Sprinkle the 1/2 t. salt evenly over the batter. Using a butter knife, swirl the salt into the batter. Bake in center of oven for about 35 minutes, until the edges are set but the center is still a bit soft and a toothpick inserted in center comes out coated with a little of the batter. Let cool at room temperature in the pan for 1 hour, then refrigerate just until firm, about 1 hour longer. Lift the brownie from the pan and peel off the foil. Cut into 16 squares, sprinkle with sea salt if desired and serve the brownies at room temperature. The brownies can be refrigerated in an airtight container for up to 3 days and frozen for up to 1 month. Makes 16 brownies.
This recipe requires a flaky sea salt, like Maldon, because the flavor is mild and the salt melts so nicely into the batter.
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