Method

Heat the oil in a large deep frying pan over a low heat.
Add the onions with a generous pinch of salt and cook slowly for around 15-20 mins. Stir occasionally to prevent them from sticking or burning until they become soft and a golden caramel colour.
Add the sugar and vinegar to give them that sweet, slightly sharp chutney vibe. Keep cooking on a low heat for another 5 mins, stirring occasionally until the mix is sticky, the sugar has dissolved and the vinegar has reduced.
Your onions are now ready to serve, or to use in a recipe.