Line a 9 by 13-inch baking pan with parchment paper. Cut parchment to fit the pan with a slight overhang on all sides. Set aside.
In a large pot on medium heat, melt the Velveeta, butter, chocolate chips, and corn syrup and whisk until combined. Remove from the heat.
Add the powdered sugar to the pot one cup at a time, stirring to combine with the chocolate cheese mixture. Work quickly so the fudge doesn't set.
Mix in nuts and vanilla extract.
Pour the mixture into the lined pan and smooth top with a spatula. Refrigerate for at least 3 hours or until firm before cutting into 1-inch* squares.
Notes
Storage: Store in an airtight container at room temperature for up to a week or in the refrigerator for about 2-3 weeks.Freezer: To freeze, wrap it tightly in plastic wrap or aluminum foil, then place it in a freezer-safe container or bag. It can be frozen for up to 3 months. When you’re ready to enjoy it, thaw the fudge in the refrigerator overnight and allow it to reach room temperature before serving.*This is a 9 by 13-inch baking pan, so in theory, you'd end up with 117 cubes, but I find the slab of fudge shrinks a bit as it sets, so slicing this as if it were 9 by 12 gives you 108 squares.