For the popcorn:
For the butterscotch:
Pour the oil and corn into a Pyrex® stewpot. Stir and put the lid on and heat over medium-high heat. Stir the pot from time to time. When the popcorn starts to pop, lower the heat a little to prevent burning. Continue to stir the pot. Remove from the heat and remove the lid when the popcorn has finished popping.
Place butter in a saucepan over medium heat. When it begins to melt, add the brown sugar. Cook for 8 to 10 minutes, stirring regularly. Then add the salt and the yeast. The mixture will foam and change colour.
Pour over the popcorn while stirring to distribute the caramel. Spread them out on a baking sheet to separate them so that they do not stick together when they cool.