In a saucepan, melt together the butter and the cocoa powder. Let cool slightly. Meanwhile, in a large bowl mix the eggs, sugar and vanilla. Add the cocoa mixture. Stir in the flour and mix well. Add nuts. Bake in a greased 9" x 13" pan at 350 degrees for 35 - 40 minutes. Dust with confectioners sugar.
Not a NESTLÉ®-tested recipe.