In a heavy bottomed pot, heat the oil over medium heat. Place one or two popcorn kernels into the pot. Once they pop, add the rest of the popcorn plus the butter and salt. Gently shake the pot to coat the kernels. Loosely tent the pot with a sheet of aluminum foil and punch a few holes in the foil.
Allow the popcorn to pop, keeping the pot tented with foil, gently shaking the pot back and forth on the burner. Once the popping slows to 2-3 pops per second, remove the pot from the heat and uncover. Transfer popcorn to a large bowl.