Lay pastry sheets on a flat surface, evenly split mince mixture over the sheets of pastry, then spread out so it almost reaches the edges. Sprinkle over an even layer of red onion before adding the cheese slices.
Roll tightly into a log shape and cut into 9 even slices. Place on a tray and pierce with a couple of toothpicks to hold its shape. Place in the oven and bake for 30 mins until cooked and golden brown.