Pour oil into the bottom of a large pot and add popcorn. Heat over medium-high heat.
Place a tight fitting lid onto the pot but leave a space on one side for steam to escape.
Pop the corn.
When the popping slows down turn off the heat.
When it's all popped, pour into a large bowl and season with salt.
Pour sugar into a small pile in the center of a saucepan and add a half-cup of water around the outside.
Heat the mixture over medium heat.
The sugar and water will form a syrup and begin simmering.
The water will evaporate and leave behind pure sugar syrup which will then begin to brown.
Do not stir during this process, as the sugar may crystallize.
When it has reached a deep golden colour, add the butter.
Whisk until all the butter has been incorporated and the Butterscotch is smooth.
Pour over popped corn and stir well.
Let butterscotch harden and then serve.