I'm a big fan of starting soups off by caramelizing a metric fucktonne of onions. Like seriously, way the fuck more onions than seems possible or even like a good idea. Assuming we're talking about a big pot of soup here, I'd dice about 7-8 onions (I like vidalia the best, but white could work too, or even a mixture - I use yellow, white and red onions for one of my onion soups) and chuck 'em into the pot with some olive oil and plenty of salt, put it on a low heat and let 'em sweat, stirring often. At this point I like to add plenty of black pepper and maybe some herbs. Once the mixture is golden brown, I'd add 5-6 cloves of very finely minced garlic. Stir well for a minute or two, so the garlic doesn't burn at all, then add some stock and bring the heat up some. From there, your options are almost limitless. You have the base of a soup that can become whatever you want. Could almost be eaten as is, but will also happily cook for almost any amount of time you need to add whatever else you like.