Preheat the oven to 190°C.
Wash and dry and the sweet potatoes and put them on a lightly oiled baking tray. Bake them for about 35-45 minutes, until the middle of them is soft (poke them with a skewer). Let them cool.
Meanwhile, finely slice the onion. Heat the oil a frying pan and gently sauté the onion & oregano for 8-10 minutes until soft. Add the balsamic vinegar and honey- turn up the heat and stir for a couple of minutes, until sticky and caramelised. Set aside.
Cut the potatoes in half and scoop out the flesh into a bowl. Add the onion mixture, season and combine. Add the dried chilli flakes, if used.
Cut the halloumi into 2cm cubes. Add a drop more oil to the pan and brown the halloumi cubes on each side. Add these to the mash and combine.
Fill the potato skins with the mixture and bake for 10-15 minutes until golden.
Serve warm with some fresh herbs scattered over them.