Caramelized onions are so good. A dish of them with a bit of toast and brie is my current answer in the last meal game. When they’re cooked perfectly they can be a revelatory experience. Complex, creamy, hugely flavorful and all it is is onions and butter.
There’s no better way to do this than the one described in the Bouchon cookbook, so that’s the method I’ll bring to you here.
8 vidalia or maui onions. Slice thinly and evenly. Evenly is important. You don’t want them to disintegrate completely but you don’t want noodles either. Use a mandoline if you’ve got one. Pot on medium-high heat, a few knobs of butter, a sprinkle of salt.
I will add one thing to Bouchon’s method, which is a cheesecloth sachet containing a couple sprigs of thyme and a few broken up pieces of star anise. As star anise cooks with caramelizing onions, they make a compound together that makes meaty things taste meatier. It’s a magical effect. Try it with rilette* sometime.

Lower the heat. Regulate it so they just bubble gently. Stir every fifteen minutes. After an hour or so you can turn it up a bit, but keep it pretty low. This is going to take between four and five hours, no kiddin’, stirring every fifteen minutes. It takes this long because you want them to be thoroughly caramelized, not just on the surface but all the way through. It’s not labor intensive, but you have to pay attention and you’ll have a better result if you happen to enjoy what you’re doing. You can read a book, watch a Futurama marathon and stir during the commercials, whatever it takes.

This is not a completely finished batch. They should be darker and more evenly darkened than this.
Watch them carefully toward the end. Most of the moisture’s been cooked out and they’re more likely to brown rather than caramelize here. You don’t want Maillard browning, which would make them bitter. Be sure to scrape out the corners of the pot as you stir or else you’ll get onion cooked on as I have above.
* I will be posting a recipe for that soon too.
I’ve pushed my sidekick’s post down unfairly with these last two. Crawl down there and read it. Watch this movie. It’s good stuff.