Twenty-four-hour caramelised onions

This is a recipe for caramelised onions in the slow cooker. On the hob, onions take time to caramelise, maybe forty-five minutes or so. You have to keep stirring, so it gets boring. In this recipe, they get a full nychthemeron in the slow cooker and the natural sugars in the onions really come out over that time. The result is a large quantity of soft, sweet and sticky onions. You can then use them on salads, burgers, toast and a bunch of other stuff, or even for a version of French onion soup. The ingredients cost next to nothing, and you might even have them hanging around because you bought or harvested too many onions for another recipe.

For the variant with sugar and vinegar:

  1. Chop the onions into semicircles at the thickness you like, but not very thin. I cut them about 5mm thick.
  2. Tip the chopped onions into the slow cooker and mix in the olive oil so that all of the onions are coated in it.
  3. Cook on low for the first twelve hours. A lot of liquid will be released and your house will now smell of onions. The first couple of times you try this recipe you should keep an eye on the proceedings just to make sure the onions don't stick or burn.
  4. After the first twelve hours, you can add some sugar if you'd like it to taste a bit sweeter. I don't find that it's necessary, though. You can also add the balsamic vinegar.
  5. Give the onions a good stir and cook on low for the next twelve hours. During this stage, ideally at the end, if the mixture looks like it has too much liquid, prop the lid open for a few hours to let it reduce a bit.
  6. Allow the onions to cool and put into jars for the fridge.
  1. Can we add shallots or garlic? I have loads of both of these left over from other recipes quite a lot of the time.
  2. Should we deglaze the bottom of the pot with a splash of stock, wine, beer, vinegar or water? We do this for non-stick pans, so maybe it's not needed in a slow cooker.
  3. Should we add the following too to see if it tastes better? Other vinegars (apple cider vinegar); Dried fruit (raisins or sultanas); fresh fruit (apples or citrus juice); herbs (thyme, parsley); spices (cinnamon, coriander, ginger, turmeric, saffron, harissa, sumac, pepper, mustard, tamaring paste); alcoholic drinks (wine, cider, Guinness); different sugars (pomegranate molasses, honey); vegetable stock, Marmite (but not Vegemite, it's revolting.). Reading around a bit, Tfaya from Morocco sounds like it's caramelised onions with extra ingredients, for example as a confit with raisins.
  4. Would it be wearisome to call these 'nychthemeronions'? Are such portmanteaux trite and unfunny?

Rick sent me a link to a page with lots of discussions about caramelised onions, and the only way to prepare them.