In a cup or small bowl, mix together the unpopped popcorn and oil. Pour the coated corn into a brown paper lunch sack, and sprinkle in the salt. Fold the top of the bag over twice to seal in the ingredients. Cook in the microwave at full power for 2½ to 3 minutes, or until you hear pauses of about 2 seconds between pops. Carefully open the bag to avoid steam, and pour into a large bowl. -- OR -- Pop corn in an air popper per instructions.
Spritz the popcorn with butter flavor PAM and white truffle oil, in desired amounts. Start with TINY amounts and toss the popcorn as you spray. A little bit of the truffle oil goes a LONG way…
Toss the popcorn with additional salt or some grated Parmesan cheese after the oil is sprayed on, if desired.
(Tip - One of those small plastic squirt bottles found in the “vacation miniature toiletries” section works just as well as a genuine oil mist sprayer… but it should be opaque and not clear if you store the truffle oil in it for a time).