Use oil to pop the kernels and butter to season the finished popcorn. Whole butter contains water and milk solids, which make it less reliable for the sustained heat of popping and can soften crisp popcorn when added heavily.
Choose the popping oil
Refined coconut, canola, vegetable and avocado oil all work, depending on the flavour and heat level you prefer. The oil must coat the base of the pot and transfer heat evenly to the kernels.
Coconut oil is solid at many room temperatures and gives a familiar cinema-style aroma. It behaves differently from liquid vegetable oil in baking, which is why it has its own coconut oil conversion guide.
Control the heat
Add a few test kernels to the oil and cover the pot. When they pop, add the remaining kernels in a single layer, cover and shake periodically. Regulate the heat so popping stays active without scorching the oil or the first popped pieces.
Remove the pot when the interval between pops stretches to a few seconds. Waiting for every final kernel usually burns the popcorn already open.
Add butter without making popcorn soggy
Melt butter gently and allow the foam to settle. Drizzle it in a thin stream while tossing the popcorn, rather than pouring it over one spot. Use enough for flavour but not so much that water collects at the bottom of the bowl.
Clarified butter is especially useful because most of its water has been removed. It coats the popcorn more evenly and preserves crispness better than whole melted butter.
Salt at the right scale
Fine popcorn salt adheres better than coarse crystals. Add part of the salt during tossing, taste, then adjust. Butter helps seasoning stick, but excessive butter is not required if the salt is sufficiently fine.
Oil performs the high-heat work; butter supplies the finish. Keeping those jobs separate produces more evenly popped, crisper popcorn.