1Heat oven to 350°F. Grease bottom and sides of 9-inch square pan. In 1-quart saucepan, melt butter and chocolate over low heat, stirring constantly. Cool slightly.
2In medium bowl, beat sugar, vanilla and eggs with electric mixer on high speed 5 minutes. Beat in chocolate mixture on low speed. Beat in flour just until blended. Stir in walnuts. Spread in pan.
3Bake 40 to 45 minutes or just until brownies begin to pull away from sides of pan. Cool completely in pan on cooling rack. For brownies, cut into 4 rows by 4 rows.