Heat the oil: Place a large, heavy-bottomed pot over medium-high heat and add the vegetable or canola oil. Drop in 2–3 test kernels and cover.
Pop the kernels: When test kernels pop, add remaining unpopped popcorn kernels, cover the pot, then remove it from heat for 30 seconds. Return pot to medium heat and shake gently until popping slows to several seconds between pops. Remove from heat and transfer popcorn to a large bowl, leaving unpopped kernels behind.
Add butter: Drizzle melted unsalted butter evenly over the warm popcorn. Use a large spoon or spatula to toss gently until all pieces are coated.
Season with cheese and salt: Sprinkle white cheddar cheese powder and fine sea salt over the buttered popcorn. Toss thoroughly until every piece is coated. Serve immediately.