Line a 9×13-inch pan* with parchment paper.

In a large saucepan over medium heat, mix the sugar, butter, and evaporated milk.

Bring the mixture to a boil. Leave on heat until the mixture registers 234°F on a candy thermometer (about 5 minutes).

Remove from heat and stir in chocolate chips until melted and thoroughly combined.

Add the mini-marshmallows, walnuts, and vanilla extract. Stir to incorporate.

Transfer the fudge to the prepared pan. Allow the fudge to set at room temperature (about 4 hours). To speed up the setting process, you can let it chill in the refrigerator to set.

Serve at room temperature.