Preheat the oven to 180°C, fan oven 160°C, gas mark 4. Put 14 paper bun cases into bun trays.
Heat the vegetable oil in a large heavy-based saucepan with a tight-fitting lid. Add the popping corn, put the lid on and shake the pan to coat the kernels in the oil. Put the pan over a medium-high heat. The kernels will begin to pop, and when they do, carefully shake the pan occasionally.
When the popping subsides, remove from the heat. Cool for 5 minutes.