Add the oil to a large heavy-bottomed pot and place over medium heat. Toss in 2–3 popcorn kernels and cover with the lid. When these test kernels pop, the oil is hot enough.

Remove the popped test kernels if you can do so safely. Pour in the 1/2 cup popcorn kernels and shake the pot gently so they spread into an even layer. Cover again.

As soon as you hear the first few pops, quickly lift the lid just enough to pour in the 1/4 cup sugar. Sprinkle it evenly over the kernels, then cover the pot again right away to keep the heat in.

Using oven mitts, hold the lid on and shake the pot firmly every 3–4 seconds, sliding it back and forth over the burner. This keeps the sugar from burning and helps the kernels pop evenly.

If you smell scorching or see a lot of steam, slightly reduce the heat. Maintain an active, steady popping while continuing to shake the pot frequently.

When the popping slows to about 1–2 pops every couple of seconds, turn off the heat and move the pot off the burner. Do not wait for every kernel to pop to avoid burning the sugar.

Carefully crack the lid away from you to vent steam. Immediately pour the popcorn into a large bowl, scraping the bottom of the pot with a wooden spoon or spatula to get all the caramelized bits.

While the kettle corn is still hot, sprinkle with 3/4 teaspoon fine sea salt and toss well. Taste and add more salt if desired. If using melted butter, drizzle it over the popcorn and toss again to coat.

Let the kettle corn sit for 5–10 minutes to cool and crisp up before serving.