Microwave chocolate and milk in 1½ quart bowl on high 2 minutes, stirring after 1 minute. Stir until chocolate is completely melted and smooth. Stir in vanilla, salt and walnuts. Spread in greased 8 x 4 inch or 9 x 5 inch loaf pan. Refrigerate until firm, about 2 hours; cut into small squares.
Add 1 c. miniature marshmallows to fudge with vanilla, salt and walnuts.
Recipe can be doubled; spread in greased 8 x 8 inch square pan.