Preheat oven to 350º. Stir cocoa and baking soda together in a mixing bowl. Blend in 1/3 cup vegetable oil. Add boiling water; stir until mixture thickens. Stir in sugar, eggs and remaining 1/3 cup vegetable oil; stir until smooth. Add flour, vanilla, salt and walnuts; blend completely.
Pour into greased 13x9-inch baking pan. Bake at 350º for 25-30 minutes or until toothpick inserted in center comes out clean. Cool completely and frost or sprinkle with confectioners' sugar, if desired.