Generously butter or line a cupcake pan with paper liners. Preheat oven to 350 F. 

Chop the chocolate and place it in a large, heat proof mixing bowl. Set aside. 

Next, melt or brown the butter.  To brown the butter, start by melting the butter in a medium skillet over medium heat. Stir occasionally at first. Once begins to bubble and comes to a boil, stir it constantly. It will start to foam. Continue stirring as you watch for it to turn a light, amber color and develop a nutty smell which should happen in about five minutes. Pour the brown butter over the chopped chocolate. Make sure the scrape the bottom of the pan for all the bits. 

Stir the chocolate and brown butter together until the chocolate has melted. Sift the cocoa into the butter and chocolate mixture. Whisk in the sugar and salt. Whisk in the eggs one at a time. Add the vanilla extract. Make sure mixture is well mixed. 

Fill cupcake cavities about 2/3 full with batter. Bake 14-16 minutes, until tops are set. Serve warm or at room temperature.