Marshmallow Marble-Top Fudge
["3 c. (1 1/2 pkg.) Hershey's semi-sweet chocolate chips", "4 Tbsp. butter or margarine, divided", "1 (14 oz.) can Eagle Brand sweetened condensed milk (not evaporated milk)", "1 1/2 tsp. vanilla extract", "dash of salt", "1/2 to 1 c. chopped nuts", "2 c. miniature marshmallows"]
["Line an 8 or 9-inch square pan with foil and set aside.", "In a heavy saucepan, over low heat, melt chocolate chips and 2 tablespoons butter with sweetened condensed milk, vanilla and salt.", "Remove from heat and stir in nuts.", "Spread evenly into prepared pan."]
["chocolate chips", "butter", "condensed milk", "vanilla extract", "salt", "nuts", "marshmallows"]