01 -
Line a 9-inch square pan with foil or parchment, leaving overhang on two sides. Lightly butter the lining so the fudge releases cleanly.
02 -
Add sugar, butter, evaporated milk, and salt to a heavy 3-quart saucepan. Cook over medium heat, stirring constantly, until the mixture reaches a full rolling boil.
03 -
Continue boiling and stirring for about 4 minutes, or until a candy thermometer reaches 234°F. The bubbles should stay active across the surface.
04 -
Remove the pan from the heat. Add the semisweet chocolate and stir until fully melted and glossy.
05 -
Stir in the marshmallow creme, walnuts, and vanilla until the mixture is even and thick. Work quickly before it starts to set.
06 -
Spread the fudge into the prepared pan. Cool completely at room temperature for at least 2 hours, then lift out and cut into 1-inch squares.