Heat enough oil in a large saucepan (you will later need a tight fitting lid for it) to just cover the bottom of the base.
Add a few kernels to the oil to test if it is hot enough and the kernels pop. Then add all the popcorn immediately and cover with the lid. Move the pan horizontally a few times to allow for the popcorn to distribute and get closer to the hot oil. During the entire process, regulate the heat to get the desired result. If you hardly hear any more pop noises, the popcorn is ready. Transfer to a large bowl.
Meanwhile, melt the butter in a frying pan over low heat, then stir through the Black Truffle Salt. Pour over the popcorn and toss to combine. Allow to cool, then sprinkle with the grated Parmesan.