LINE 8- or 9-inch square pan with foil, extending foil over edges of pan.
MELT chocolate chips with sweetened condensed milk and salt in heavy saucepan over low heat. Remove from heat. Stir in nuts and vanilla. Spread evenly into prepared pan.
CHILL 2 hours or until firm. Remove from pan by lifting edges of foil. Cut into squares.
COMBINE chocolate chips with sweetened condensed milk and salt in 1-quart glass measure. Cook on HIGH (100% power) 3 minutes or until chips are melted, stirring after 1 1/2 minutes. Stir in remaining ingredients. Proceed as above.
CREAMY DARK CHOCOLATE FUDGE: MELT 2 cups miniature marshmallows with chocolate chips and sweetened condensed milk. Proceed as above.
MILK CHOCOLATE FUDGE: OMIT 1 cup semi-sweet chocolate chips. Add 1 cup milk chocolate chips. Proceed as above.
CHOCOLATE PEANUT BUTTER CHIP GLAZED FUDGE: FOLLOW above recipe using 3/4 cup peanut butter chips instead of nuts. For glaze, melt 1/2 cup peanut butter chips with 1/2 cup heavy cream. Stir until thick and smooth. Spread over chilled fudge.