Preheat oven to 350°. In a small saucepan, melt butter and chocolate over low heat. Cool slightly.

In a large bowl, beat eggs, sugar, vanilla, and salt until blended. Stir in chocolate mixture. Add flour, mix well. Stir in walnuts.

Spread batter into a greased 9 inch square baking pan. Bake 40-45 minutes or until toothpick inserted in center comes out with moist crumbs ( do not over cook).

Cool completely in pan on a wire rack. If desired, dust top with confectioners sugar. Cut into bars.