Heat oven to 350 degrees. Place a baking pan half full of water in oven.
Bring a saucepan of water to barely simmering. Place chocolate and butter in a heatproof bowl. Place over water and stir until almost melted. Remove bowl from heat and let cool, stirring occasionally.
Sift together twice all the dry ingredients except sugar. Set aside.
Beat eggs and vanilla until foamy and light. Add sugar and beat until fluffy. Stir in chocolate-butter mixture. Fold in dry ingredients. Pour into five 8-ounce custard cups, filling each nearly to rim. Place in baking pan; water should come halfway up sides of cups.
Bake for 30 minutes or until brownies have risen to just above the rim and tops are cracked. They should be firm to the touch. Let cool for 5 minutes, then serve dusted with confectioners’ sugar.