Preheat oven to 350. Line 13x9 inch baking pan with foil,with end of foil extending over side of pan. Grease foil.
Microwave chocolate and butter in large microwave bowl on HIGH 2 min.or until butter is melted. Stir until chocolate is melted.Stir in sugar, eggs and vanilla.Add flour and nuts mix well.Spread into prepared pan.
Bake 30-35 min. or until toothpick inserted in center comes out with fudgy crumbs.(DO NOT OVERBAKE)Cool in pan on wire rack.Remove from pan with foil handles. Cut into squares. Store in Tightly covered container.