6 oz Chocolate, semisweet
4 ea Egg whites
2/3 c Sugar
1 ts Baking powder
1 ea Icing sugar
1/2 c Hot water
1 ts Vanilla
2/3 c Flour, all-purpose
1 pn Salt

In large heatproof bowl set over hot water, melt chocolate with water, stirring until smooth. Remove from heat; let cool slightly. Whisk in egg whites and vanilla. Stir together sugar, flour, baking powder and salt; stir into chocolate batter just until combined. Pour into lightly greased 8 in. square cake pan. Bake in 350F oven for 20 to 25 minutes or until edges pull away from pan. Let cool on rack; dust with icing sugar.