Thinly slice onions and shallots. Add to a large pot and drizzle with olive oil. Sautee over medium heat, stirring often, for about 5 minutes or until onions have begun to soften and become slightly translucent.
Turn stove down to low heat and stir in thinly chopped or minced garlic. Continue sauteeing for 1-2 minutes or until garlic becomes fragrant. Mix in remaining ingredients.
Reduce heat until the chutney is barely bubbling and cook down for 60-90 minutes, stirring occasionally until onions have absorbed most of the liquid.
Notes
Save time (and tears) on this step by using the slicing disk on a food processor.
You can technically turn up the heat to reduce the necessary cooking time, but I recommend the low & slow approach as this will reduce the risk of your onions burning and getting stuck to the bottom of the pan.
Dice the onions, rather than thinly slicing them if you prefer more of a spreadable jam-like texture.
The flavor of this red onion chutney will continue to deepen over time. Some say it's best to leave it for 2-3 months to get the best flavor out of it!
Store in a sterilized jar and keep in a cool, dark pantry. It should be good for up to 1 year, possibly even longer.
Once opened, you can keep it in the refrigerator for up to 2 months.