Onions and other alliums"Good cooking is impossible without onions."
They can be caramelized in several ways. A cast iron skillet over a flame, or in the oven. The pan must be well-seasoned, as the oil of the onions will soften its surface fairly quickly. If you want to use something besides cast, non-stick plastic is fine, except it kills every bird in your house the first time. No one knows what it does to us mammals yet. Stainless is OK, but it better be thick, like enameled or with copper or something. Thick aluminum is good too, as long as it's clad with something else which keeps your food from ever touching it, (and which is not even more toxic.) A cast pan must be much thicker and heavier to equal the more even heating of other metals, but once it has a proper finish it's as slick as teflon.
Getting back to onions, to caramelize them use some oil (olive?), start hot, stir frequently, let them brown a little as they become translucent, and then reduce to a low flame. Cover. Stir as often as it takes to keep them from even almost sticking. Be patient, onions have a lot of sugar in them. I usually resort to deglazeing them with a little white wine, or sometimes balsamic vinegar if the dish likes to be sour. Just get them brown.
Be very careful not to "over-caramelize" any allium, whether onions, shallots, leeks or garlic. Onions can take a moderate char, shallots and leeks a little, but garlic almost none. Slightly burnt garlic ruins any dish.
Another very important point about alliums is that their "heat" is created by contact with air. Few cooks seem to understand this. I sometimes use a whole bulb of garlic where others might use a clove. If you throw all the whole cloves into the oil (Don't burn them!), or the sauce, it will be milder than one clove minced or put through a press. The whole cloves will still have their sweetness and earthy aroma, but their heat is gone.
I'm eating a griselle shallot as I write this, with pissaladriere. The shallot is leeky, then hot garlic - multiplier onion, then the aboriginal allium aftertaste. Wow!
My mother used to complain that I stunk of onions when I came back from camping. My Dad and uncles and I ate hot cooking onions like apples, to help fend off mosquitos, and they stayed on my breath and sweat for days. Now I want a shallot a day! Raw!
I want to reek of them for the rest of my life