Mix the base: In a saucepan, combine sugar, evaporated milk, butter, and salt. Stir over medium heat for about 5 minutes until smooth and well blended.
Add the chocolate: Stir in chocolate chips and cook until fully melted and creamy.
Incorporate marshmallows and flavor: Remove from heat. Add marshmallows, vanilla, and walnuts. Stir until marshmallows soften and everything is evenly combined.
Shape the fudge: Pour the mixture into an 8-inch square pan. Allow to cool, then cut into squares.
Serve and enjoy: Each piece is a perfectly sweet, nutty bite of fudge heaven.