Melt butter in a saucepan, add cocoa and stir. Sift flour, salt, baking powder in an other bowl.

Beat eggs with sugar for one minute, with beater on low speed. Add vanilla, Melted butter & cocoa mixture to the egg mixture, then add flour and mix until smooth.

Line a 13x9 inch pan with wax papper. Pour mixture in the pan. spread equally. Sprinkle chopped walnut on the top. Bake in preheated oven for 30 minute at 350 F or until a toothpick inserted near the center comes out clean (do not overbake). Cool on a wire rack. When cool cut into 24 pieces. Enjoy.