Foolproof Dark Chocolate Fudge

18 ounces semisweet chocolate chips
14 ounces sweetened condensed milk
Dash of salt
1/2 to 1 cup chopped nuts
1 1/2 teaspoons vanilla extract

In a heavy saucepan over low heat, melt chips with sweetened condensed milk and salt. Remove from heat; stir in nuts and vanilla extract. Spread evenly into a wax paper-lined 8- or 9-inch square pan. Chill 2 hours or until firm. 

Turn fudge onto cutting board; peel off paper and cut into squares. Store loosely covered at room temperature.