Chocolate Fudge
["2 c. semi-sweet chocolate chips", "2 oz. bittersweet chocolate, cut into 1/2-inch pieces", "14 oz. can sweetened condensed milk", "2 1/2 tsp. pure vanilla extract", "1 c. chopped nuts (optional)"]
["Line an 8-inch square baking pan with waxed paper. Place chocolate chips, bittersweet chocolate and condensed milk in a double boiler over hot water. Stir until all melted. Stir in vanilla and nuts. Spread fudge into prepared pan. Refrigerate until firm."]
["semi-sweet chocolate chips", "bittersweet chocolate", "condensed milk", "vanilla", "nuts"]