Line a large rimmed baking sheet with parchment paper; set aside. Add oil and 2 individual corn kernels to a wide 6-quart heavy-bottomed pot of Dutch oven, cover with a lid, preferably clear. Heat over medium-high heat, without moving or lifting lid, until both kernels pop and oil is hot (around 390°F), 3 to 4 minutes.
Add remaining corn kernels to pot, and gently stir to coat all kernels; sprinkle sugar and salt over kernels and gently stir to evenly coat. Cover with a lid, keeping lid slightly ajar by about ½ inch. Swirl the pot to move kernels around, lifting and swirling pot every 2 to 3 seconds until sugar is melted and kernels start to pop, 4 to 5 minutes. Once kernels begin to pop frequently, continue shaking pot, holding lid on tightly (but still slightly ajar), every 4 to 5 seconds, until popping slows down to 2- to 3-second intervals, 2 to 3 minutes total time.
Remove pot from heat; vigorously shake pot, holding lid on tightly. Let stand for a few seconds until popping stops. Pour popcorn onto the prepared baking sheet. Let cool for 5 minutes before transferring to a bowl and serving.
