The way my Italian (Sicilian) grandpa taught me when I was 5 is: use a flat-bottomed wok-type pan with a tight cover (he actually had a popcorn popper), put in just enough oil to seat, but not cover, a layer of popcorn, heat to medium. While it’s heating, place 5 fat kernels in.
When the last of the 5 kernels pop, (oil is ready), put one layer in the pan, crowded together but not on top of each other. Shake to level kernels. Start quaking the pan on the burner when they start to pop, don’t stop until the popping stops, then wait for the last five kernels to pop, still quaking. 100% popped popcorn, remove from fire.
You can drizzle ice-cream caramel topping and fresh ground sea salt, or a pack of the powdered cheese from a box of mac&cheese, or garlic salt and parmesan, or just butter and salt.
i use a heavy pan... i do use medium heat... i cover the kernels in the pan with a lid, but leave it a little off so there is a slight opening... i do not shake the pan... just leave it be... and i let them pop, pop, pop... after that is done, i pour the popcorn into a brown paper grocery bag... i toss in the sea salt and pour in the butter... i shake the bag and let it all coat the popcorn... then i pour it all into a big bowl...