Why does steam come out when you first open a container of hot popcorn? Be extra careful when opening a bag, foil dome, or even removing the lid off a pot of freshly made popcorn! Why? The water vapor ...

Keep popcorn warm in the oven while making the caramel mixture. Butter a large piece of foil and set aside. For caramel, in a medium saucepan, combine brown sugar, butter and corn syrup.