In medium saucepan, melt chocolate and margarine over low heat, stirring constantly. Stir in corn syrup and vanilla; blend until smooth.* Add 1 cup powdered sugar and graham cracker crumbs; blend well.
Turn mixture out onto waxed paper; knead in 1/3 cup powdered sugar and walnuts. Divide mixture into 4 equal parts. Roll each part into 10-inch log. Cut each log into 10 equal pieces. Wrap each piece individually in waxed paper or plastic wrap.