Heat oil in a small pan and cook onion until soft and starting to brown. Put to one side and allow to cool slightly. In a bowl place the pork mince, apple sauce and onion, and mix together. Take a slice of apple and mould the mince around the slice, leaving the top of the apple exposed, mixture should make sufficient for 5 burgers. Place on a sheet of foil, cover and leave in the fridge for about 30 minutes to cool and set. Meanwhile heat the BBQ, making sure the coals are hot and ?grey' before you start cooking. Alternatively if it starts to rain preheat the grill. Place the burgers (on the foil) on the grill grid - make some holes in the foil to allow juices to run away. Cook for 15 minutes or until cooked through, carefully turning half way during the cooking time. If the outside of the meat starts to catch, cover with foil and adjust the grid height to move away from the heat to slow down the cooking. Serve with crusty, chunky bread slices, salad leaves and BBQ sauce. Cook's tip: there are two ways of using the cheese; for cheese topped burgers add cubes of cheese to the ?almost' cooked burgers and allow to melt either on the BBQ or flash under a hot grill. Alternatively for ?cheesy burgers' add smaller cubes of cheese to the pork mince mixture before shaping into burgers.