Line an 8 inch square pan with foil or parchment paper.
Combine in a medium sauce pan sugar, evaporated milk, butter and salt.
Bring to a FULL ROLLING BOIL and stir constantly at a boil for 4-5 minutes.
Stir in marshmallows, chocolate chips, and vanilla.
Stir vigorously for one minute or until marshmallows are melted.
Pour into prepared pan.
Refrigerate for at least 2 hours or until firm.
Cut fudge into pieces. Enjoy.