Line 8-by-8-inch pan with foil, leaving overhang on sides to remove fudge later.

In medium saucepan over medium heat, combine condensed milk, caramel and white chocolate chips. Stir constantly with wooden spoon or rubber spatula until chips are melted and mixture is smooth. Remove from heat. Stir in vanilla and salt. Cool mixture 10 minutes.

Slowly and carefully fold in chopped Twix bars (to keep chocolate swirl intact). Pour and spread mixture into prepared pan. Cover pan with foil and refrigerate 4 hours or store at room temperature overnight.

Remove fudge from pan using foil as handles. Use sharp knife to cut fudge into 64 1-inch squares (if fudge has been refrigerated longer than 4 hours, let fudge sit at room temperature 20 minutes before cutting).