My grandchildren prefer this to the real buttery mix at the farmers market on Saturdays.
Heat a large, deep pot to medium-high heat. Add oil and popcorn. Cover tightly with lid and cook until kernels just begin to pop, 3-4 minutes. Give pot an up and down shake every 30 seconds or so. When popping has almost stopped, remove pot from heat. Turn heat to low and add sugar and salt to popcorn. Return pot to heat until the sugar has melted, shake 5 or 6 times in an up and down motion to coat the popcorn. The sugar should be melted and beginning to caramelize. Take a long wooden spoon and mix popcorn to make sure it is separate kernels from bottom of the pot. Pour into a large bowl and serve.