Foolproof Dark Chocolate Fudge

Makes about 2 pounds. In heavy saucepan, over low heat, melt chips with sweetened condensed milk and salt. Remove from heat, stir in nuts and vanilla. Spread evenly into 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. Microwave: In 1-quart glass measure, combine chips with sweetened condensed milk. Microwave on full power (high() 3 minutes. Stir until chips are melted and mixture is smooth. Stir in remaining ingredients. Proceed as above. Creamy Dark Chocolate Fudge: Melt 2 cups miniature marshmallows with chips and sweetened condensed milk. Proceed as above. Milk Chocolate Fudge: Omit 1 (6 ounce) package semi-sweet chocolate chips. Add 1 cup milk chocolate chips. Proceed as above. Creamy Milk Chocolate Fudge: Omit 1 (6 ounce) package semi-sweet chocolate chips. Add 1 cup milk chocolate chips and 2 cups miniature marshmallows. Proceed as above. Mexican Chocolate Fudge: Reduce vanilla to 1 teaspoon. Add 1 Tablespoon instant coffee and 1 teaspoon ground cinnamon to sweetened condensed milk. Proceed as above. Butterscotch Fudge: Omit chocolate chips and vanilla. In heavy saucepan, melt 2 (12 ounce) packages butterscotch flavoured chips with sweetened condensed milk. Remove from heat; stir in 2 Tablespoons white vinegar, 1/8 teaspoon salt, 1/2 teaspoon maple flavouring and 1 cup chopped nuts. Proceed as above.