In a glass mixing bowl, combine butter and baking chocolate. Microwave butter and chocolate until melted (on HIGH about 2 minutes).
Stir sugar into chocolate until well blended. Stir in eggs and vanilla. Mix in flour. Stir in nuts and bar chocolate. Gently fold in. Do not over mix. Pour into a 9 x 13-inch buttered baking dish and bake 30 to 35 minutes and 350 degrees F (325 degrees F in glass pan), until wooden pick in center comes out with fudgy crumbs.Makes 1 to 2 Source: