Heat oil in a deep saucepan over medium, and add three popcorn kernels.
When the kernels pop, the oil is ready. Pour in the rest of the kernels and shake pan to evenly coat kernels in oil. Continue shaking every few seconds to help the kernels pop. Once the popping slows to 1-2 every 10 seconds, pour popcorn into a large bowl.
Melt butter in the microwave or in a small saucepan, and whisk in pesto.
Drizzle butter mixture over the popcorn to taste and stir to coat, then sprinkle on salt and Parmesan and stir again. Serve!
Notes
You might not use all of the pesto butter; add it a bit at a time until coated to your liking.