Spray an 8-inch square baking pan with vegetable spray.
In a large mixing bowl whip the egg whites until frothy. Gradually add sugar and beat until fluffy.
Meanwhile, stir the oil into the melted chocolate. Add this mixture to the egg whites and blend.
With a mixer on low, sift in the flour and cocoa powder and fold together. Beat until fluffy. Add Yogurt and vanilla extract, beat to combined.
Scrape the batter into pan, smooth top. Bake at 350º, (Note) until batter in the center feels firm to the touch (you don't want a dry bar, but very moist. . . about 35 minutes.
Cool to room temperature. Cover with plastic wrap, and chill until firm, at lease one hour. Cut up into bars.
Recipe submitted by Nick on 8/16/00