This recipe was very popular during the Second World War when people wanted to ship goodies to their soldiers overseas. It travels well, lasts a long time and contains no sugar as sugar was rationed during the war.
Heat milk, chocolate chips and baking chocolate over low heat stirring constantly until chocolate is melted and mixture is smooth, remove from heat. Add the vanilla extract and nuts, if using. Spread into pan and chill until firm. Cut into 1-inch squares.