Heat the oil in a large saucepan and gently fry the onions over a low heat for 25-30 minutes until softened but not browned. Stir in 3 tbsp sugar, increase the heat and cook for 3-4 minutes, until the onions are browned, then add the remaining sugar and all the other ingredients.
Simmer gently for 45 minutes to 1 hour minutes until the liquid has reduced and the mixture has thickened and become a dark caramel colour.
Spoon the hot chutney into cooled, sterilised jars, then seal and label. Store for up to 6-12 months.
Cook's note: This chutney is fantastic with grilled meats, especially sausages, and a spoonful added to pan juices helps make a great gravy for roasts.