Servings: Makes 12 brownies
Preheat the oven to 350°. Coat an 8" x 8" baking pan with cooking spray.
Melt the chocolate in a double boiler or over a very low flame.
In a large bowl, combine the melted chocolate, vegetable purees, sugar, cocoa powder, margarine and vanilla and whisk until smooth and creamy, 1 to 2 minutes.
Whisk in egg whites. Stir in the flour, baking powder, and salt with a wooden spoon.
Pour the batter into the pan and bake 35 to 40 minutes. Cool completely in the pan before cutting into 12 bars.