I shared my discovery of this method of making caramelized onions a few days ago yesterday. tldr: you cook several pounds of onions with butter and salt for 4-5 hours on low heat stirring very regularly.
I sacrificed 4 hours to the crying onion god today. From my first cut onion to turning the stove off, it took 4 hours and twenty minutes. I was scared of ruining them so I kept the heat slightly lower than I could have (meaning I think I could get them done slightly under 4 hours). I also added 3 heads of garlic to the process because I didn't want to prep garlic separately.
They are so good that I suspect I've never had real caramelized onions before today. Mother fracking yum ya'll. The result is onions that taste like toffee or toffee that tastes like onions. And I love onions. And toffee (although I rarely eat it).
You could probably charge $20 for a small jar of this, and it's probably pretty shelf stable if jarred properly. If I had a stall at a farmer's market it's probably what I'd sell (along with things made with the onions).
It's basically the best condiment ever and I plan to add it to my meals as I describe in my meal prep post. I'm also curious what other uses I might find for it. I suspect it'd be great in a fine ice cream - some herb or fruit base (a lean-in one like fig, an obvious one like strawberry, or a subtle one like melon), goat cheese, and the onions.
I give it five meat morsels on the k00bimeater.