Makes 64 pieces
4 cups sugar
1 ⅓ cups milk
¼ cup corn syrup
¼ tsp. salt
4 oz. unsweetened baking chocolate
¼ cup butter
2 tsp. vanilla extract
1 cup coarsely chopped walnuts, if desired

In a medium saucepan over medium heat, combine sugar, milk, corn syrup, salt and chocolate; cook, stirring constantly, until chocolate is melted and sugar is dissolved. Continue cooking, stirring occasionally, until mixture reaches 234° on a candy thermometer or until a small amount of mixture dropped into a cup of very cold water forms a soft ball that flattens when removed from water; remove from heat. Stir in butter. Cool mixture, without stirring, to 120° (about 1 hr.). Add vanilla; with a wooden spoon, beat vigorously and constantly until mixture is thick and dull (5-10 min.). Stir in nuts; spread in a buttered 8x8" baking pan. Let stand 1 hr. or until firm before cutting into 1" squares.