Grease an 8x8-inch square pan and line with parchment paper. Let the ends of the paper hang over the edge. Grease the paper or foil.

Using a double boiler, melt chocolate, stir until smooth, add milk, powdered sugar and salt together over low heat. Stir occasionally.

Remove from heat and add the vanilla and nuts if using. Scrape the mixture into the prepared pan. Let set in a cool place for 2 or 3 hours. For easy cutting, remove fudge from pan by lifting out using the overhanging paper. Cut into squares and serve. Store remaining fudge in tightly covered container.

Makes 25-36 pieces.