In a small saucepan melt the butter and cocoa, stirring as it melts. Remove from heat.
In medium bowl, beat eggs until frother. Add sugar, flour, nuts and salt. Don't stir yet. Pour cocoa mixture over top and stir all together. Scrape batter into greased 8X8 inche (20cmX20 cm) pan. Bake in 350 degrees F for about 30 minutes untilo the edges begin to show signs of pulling away from the sides of the pan. Frosting optional.