Chop the onions as fine as you like and cook them in a little oil until they're soft. Add them, along with everything else, to your big, nonreactive, heavy-bottomed cooking pot. Bring the mixture to a boil and then down to a simmer. Continue to simmer until the onions are translucent and the liquid has nearly evaporated. This may take as long as two hours.
I learned a neat trick for determining whether your chutney is done. It comes from Thane Prince's, Jellies, Jams & Chutneys. (I seem to be fully on-board with the Brits for this recipe.) Drag a wooden spoon through the mixture, across the bottom of the pan. If it leaves a clear path, with only a little liquid running back, you're all set.
When jarring this recipe, you'll notice lots and lots of air bubbles. I worked around the sides with my little spatula to release them. I allowed 1/2 inch of head space and processed 15 minutes. Yielded six half-pints.