Finely chop the onion and figs.
Heat the oil in a heavy-based saucepan over medium heat, then add the onion and sauté for 5 minutes. Add a small spoonful of sugar and balsamic, then stir for a couple of minutes to caramelise.
Add the chopped figs and a splash of water. Put the lid on and cook for 10 minutes over low heat. Add the balsamic vinegar and sugar then cook for another 10 minutes, under cover.
The figs should be soft now, if not, mash them with a fork.
Turn up the heat and reduce it until all the liquid has evaporated and you a get a jam-like, sticky chutney.
Let it cool, then transfer it into a sterilized jar or you can serve it immediately.