Prepare a pan with parchment paper and non-stick spray. You can use a 9x13 pan if you want thinner fudge pieces. If you like thicker pieces, use an 8x8.
Add the butter, white sugar, and evaporated milk to a saucepan and heat over medium heat.
Heat and stir until the mixture comes to a full boil. Once the mixture comes to a full rolling boil, stir continuously for exactly 5 minutes then remove from heat.
Stir in the chocolate chips, vanilla, and salt until you see no more lumps.
Stir in the marshmallow creme until fully incorporated then mix in the walnuts.
Add the mixture to the prepared pan and smooth with spatula. Sprinkle with more walnuts on top.
Allow the mixture to cool at room temperature for 4 hours or in the fridge for 2 hours. Serve at room temperature.