Melt one stick of butter with the four ounces unsweetened chocolate. Let cool. Cream the remaining one stick of butter with sugar, salt, and cake flour. Add the eggs slowly and blend until smooth. Add the melted chocolate mixture, the vanilla and the walnuts. Fold in by hand with a rubber spatula. Spray sides and bottom of an 20 cm square pan. Pour the brownie mixture into the pan and spread out evenly with your spatula. Bake at 350 degress for 30 to 40 minutes. You may also use a 9-by-13 pan, but brownies will be thinner. Adjust your time accordingly. Cool and cut into dozen servings. Top each brownie with a whole walnut and drizzle with melted semisweet chocolate. Serve cold or warm with ice cream and hot fudge sauce. Recipe can be doubled. Use a 12-by-16-by-1 inch pan.