This is my absolute favourite preserve and we get through loads of it!! Its a pain having to chop all the onions (I have a mandolin so that makes it easier). I have tried using frozen ready diced onions but it was gross!!!
100ml olive oil
2kg onions - peeled and thinly sliced
200g demerara sugar
150g redcurrant jelly (or cranberry sauce)
300ml cider vinegar
50ml balsamic vinegar
1 tsp salt
1/2 tsp black pepper
Heat the oil in a large pan and add the onions. Reduce the heat, cover the pan and cook on a low heat for approx 40 mins, stirring occasionally. The onions need to be collapsed and beginning to colour.
Add the sugar and redcurrant jelly. Increase the heat and stir more frequently for approx 30 mins until the mixture turns a dark nutty brown and most of the moisture has gone.
Take it off the heat and let it cool for a couple of minutes (very important) and add the vinegars. Put it back on the heat and cook rapidly for approx 10 mins until it becomes gooey and the spoon test works (see green tomato chutney recipe).
Remove from the heat and put in jars (approx 5 x 225g jars). You can use it straight away and it lasts for approx 12 months. It is fab with pate and cold meats.