Into a bowl sift together the flour, the cocoa powder, and a pinch of salt. In a large bowl with an electric mixer cream together the butter and the sugar and beat the mixture until it is light and fluffy. Add the eggs, 1 at a time, beating well after each addition, and stir in the vanilla. Add the flour mixture, stirring until the mixture is blended well, and stir in the walnuts. Pour the batter into a buttered and floured 9-inch-square baking pan, smoothing the top, and bake it in the middle of a preheated 350° F. oven for 25 to 30 minutes, or until it pulls away slightly from the sides of the pan and a wooden pick inserted in the center comes out with crumbs adhering to it. Let the brownies cool before cutting them into squares. COOK 028