Pour vegetable oil in a 3-quart sauce pan and rotate to cover bottom. Place pan on stove and let heat for a minute or so over medium high heat. Continuously shake the pan across the burner until popping reaches a crescendo.
Put three popcorn kernels in the pan. When one or two of them pop, cover the bottom of the pan with popcorn. Place the top on the pan ajar. The popcorn should start popping in a minute or so.
Pour truffle oil in to a large bowl and swirl to distribute evenly. Immediately add the hot popcorn to the bowl and toss gently to coat popcorn with truffle oil. Add salt to taste.