c("Combine the flour, oat bran, cocoa, sugar and salt, if desired, and stir to mix well.", "Add the sweet potato, egg whites, and vanilla extract, and stir to mix well.", "Fold in nuts if desired.", "Coat an 8-inch square pan with non-stick cooking spray.", "Spread the mixture evenly in the pan and bake at 325° for about 25 minutes or until the edges are firm and the center is almost set.", "Cool to room temperature, cut into squares and serve.")