1) Place the oil, popcorn and salt in a large 6L metal mixing bowl. Cover with heavy-duty aluminium foil and poke 10 slits in the top with a knife.
2) Place the bowl over a medium heat and shake constantly using a pair of tongs to hold the bowl. Continue shaking until the popcorn finishes popping, approximately 3 minutes.
3) Remove the bowl from the heat and carefully remove the foil. Stir in any salt remaining on the side of the bowl.
4) Melt the butter in the microwave. Slowly drizzle over the popcorn, while spinning the bowl. Serve immediately.