Preheat oven to 350 degrees F.
Prepare a cupcake pan with paper liners and lightly spray with nonstick spray. Sift the cake four, baking soda, baking powder, and salt together. Set aside.
Melt chocolates and water over low heat in a double boiler.
In a mixer with a paddle attachment, slowly cream butter and 8 ounces of sugar. Add egg yolks, 1 at a time, and beat until fluffy.
In a separate bowl, with a mixer and wire whip attachment, whip egg whites and 3 ounces of sugar until stiff peaks form.
Combine milk and vanilla in a measuring glass. Fold melted chocolate mixture into butter mixture. Alternately fold the flour mixture and milk mixture into the butter mixture. Gently fold in the whipped egg whites. Fill cupcake cups 2/3 full and bake until a toothpick comes out clean, about 15 minutes.
Recipe courtesy of Bronwen Weber, Austin, TX