Beat the butter, sugar, and eggs until fluffy. Add the chocolate, vanilla and salt and mix well. Gradually beat in the flour. Mix in 1 cup of the walnuts.
Halve the dough and shape each piece into a log 8 inches long and 2 inches in diameter. Roll each log in the remaining walnuts; wrap separately in plastic and chill until firm, about 1 hour.
Heat oven to 375º F. Grease 2 cookie sheets. Cut the dough into 1/4-inch-thick slices and place on the sheets. Bake 15 minutes or until lightly browned on the bottoms. Remove the cookies with a metal spatula and cool.
Plan ahead: Freeze the dough for up to 4 months. Thaw at room temperature 45 minutes or overnight in the refrigerator.