Place popcorn, olive oil, and salt in a large pot. Stir well. The oil should coat every kernel of corn.
Cover the pot and place over medium heat.
Shake the pot continuously back and forth over the burner. The popcorn will start popping after a few minutes. Use potholders to protect your hands from the heat.
Continue shaking the pot until you hear about 3 - 4 seconds between pops.
Remove pot from heat and transfer popcorn to a large serving bowl.
Melt butter in the microwave or in a small skillet.
Drizzle a third of the butter over the popcorn. Top with additional salt (if desired), pepper to taste, and ⅓ of the Parmesan. Mix popcorn well.
Repeat the previous step.
Finish by topping popcorn with remaining butter and Parmesan, plus salt and pepper to taste. Serve immediately.
Notes
I recommend using a heavy-bottom stock pot or dutch oven to make the popcorn.