Line an 8x8-inch baking pan with aluminum foil or parchment paper, then spray the liner... or line a mini muffin tin with paper liners. Set aside.
Combine the evaporated milk, sugar, and butter in a heavy saucepan. Bring to a boil and boil, stirring constantly, until the temperature reaches 234°F on a candy thermometer (approx. 4-5 minutes at a rolling boil).
⅔ cup evaporated milk, 3 cups granulated sugar, ¾ cup unsalted butter
After the sugar mixture reaches 234°F, immediately remove it from the heat.
Add the marshmallow cream, vanilla, and chocolate chips.
7 ounces Marshmallow cream, 10 ounces milk chocolate chips, 1 teaspoon pure vanilla extract
Pour the fudge into the prepared pan(s), top with cashews (if desired), and let set for at least 3 hours.
¼ cup whole cashews
Remove from the pan (or muffin tin) and cut into pieces.