These are excellent as an appetizer or for potlucks/ buffets. They are lovely straight from the oven but are also good cold. I include mashed potato to give them a creamy texture but they can be made with just cheese and onion as a filling.
Preheat the oven to 180 degrees C or 350 degrees F.
Lay out the puff pastry sheet.
Spread the mashed potato over the pastry, leaving a half inch gap at one end (if you have a rectangular sheet of pastry, leave the gap along one of the longer sides). This will allow the pastry to seal once rolled and stop the filling overflowing.
Spread the onions and cheese over the mashed potato, again leaving a gap.
Roll the pastry tightly towards the end with a gap in the filling.
Dampen with water the pastry where you have left a gap and use this part to seal the end to the roll.
Cut into 3/4 inch pinwheels and bake on a tray in the oven for 12-13 minutes, or until the pastry is cooked and the cheese golden.
Allow to cool slightly before removing from the tray.