In a medium saucepan, add the neutral oil and one popcorn kernel. Heat over medium-low heat until the kernel pops, about 5 minutes. Add in the rest of the popcorn and cook, shaking the pot occasionally until all the popcorn has popped. A good trick to listen for when the popping slows down and as soon as you can count 1 second between pops, turn off the heat.
Add the popcorn to a large bowl with the olive oil, salt, rosemary and truffle oil. Toss well and dig in!