Thursday, January 24, 2013

Another Sous Vide Trick: Über-Caramelized Onons

I love caramelized onions, and I love them super-duper caramelized.  When I did this for Thomas Keller's French Onion Soup, it took about 8 hours of caramelizing (stirring every 30-45 minutes) to get the onions as dark as I wanted.  That's not really an option these days.  I've heard a rumor (which I believe) that you can't caramelize onions from raw using sous vide because the gases released by the onions will make the bag explode... (I didn't want to test this...)  Instead I did a bit of a hybrid technique.  While I was putzing around in the kitchen, I threw the sliced onions in a pot with a bit of salt over medium-high heat, covered.  
(This is how I always start my onions, since it forces them to release their liquid early and thus allows faster caramelization later...)  After a good amount of liquid is rendered, you can uncover and let it cook off, stirring every now and then.  Because there is so much liquid at this stage, there's minimal risk of burning so you can totally ignore the onions for the most part...
Once the onions had given off their liquid and that liquid had mostly cooked off, I tossed them into a vacuum bag, closed the top with a bag clip, and plunged them into an ice bath to chill (since hot things do not vacuum-seal well...).  After sealing, the onions can go into a 180-degree water bath until they achieve the desired caramelization...  A couple hours for moderate...
or overnight for super-duper-crazy-caramelized... 
Pretty awesome, yeah?  Again, this is just (regular, not sweet) onions with a bit of salt... and this is totally how my onions are getting caramelized for my next batch of onion soup...

4 comments:

lester said...

OMG I love this. Thanks for the pro-tip! It's a must try!! Thank you so much!!

TFHZone said...

I followed your directions exactly and got a beautiful bag of caramelized onions that look just like yours! I'm making French Onion Soup this week and this technique is such a time saver. Thank you!

Marilyn said...

Hmm. Seems easier to me to just microwave the onions for a few minutes. I bet if you used the sous vide zip bags you could just zap them for about 5 minutes, seal and put in the water bath immediately.

Not having the sous vide bags I microwaved my onions in a glass bowl and then transferred them to a ziplock

Greta said...

Or, you could just use mason jars, and skip the cooking altogether. They let the onions burp.