Heat a cooker, add oil and 1 tbsp butter.
When butter melts, add corn kernels and mix to ensure all kernels get coated with butter, stir for a minute.
Cover the cooker with its lid, but make sure to take off the whistle.
When the corns start to pop, give the cooker a good shake once or twice to toss the popping corns.
After the corns stop popping, turn off heat and take off the lid.
Transfer the popcorn to a large mixing bowl.
Add sugar and water in a saucepan, and heat it over low-medium heat.
When the mixture becomes light brown in color, add butter. (See note below.)
Stir for a minute and then pour the caramel mixture on the popcorn. (Pour the mixture immediately as soon as it is ready because it starts to thicken real soon.)
Mix properly so that all popcorn are coated with the caramel mixture and then transfer the popcorn onto a tray lined with parchment (baking) paper.
Separate the popcorn fast before they're glued together with caramel mixture.
Allow to dry properly, and after 5-6 minutes the caramel popcorn is ready to eat.