Caramelized vegetable soup redux
October 17, 2011 
6 Comments
Autumn is undeniably soup season, not to mention squash season, which may explain why my speculation on soups made from caramelized vegetables other than carrots went so quickly from “I wonder if it would work?” to “What’s for dinner?”
I started by seeding, peeling and dicing a small butternut squash, and weighing the flesh. I decided to keep the same proportions of ingredients as in the carrot soup, scaling the squash to 100% and adding 16% butter, 1.5% salt and 0.5% baking soda. As well, tipped off by a commenter on the carrot soup post, I added a couple of tablespoons of water to the pressure cooker, sealed it and cooked it at high pressure for 20 minutes.
The results were unevenly caramelized, but fully cooked, so I pushed on. I omitted the butter at this step, looking for a leaner preparation, and added duck stock rather than squash juice. I thinned the soup by eye, aiming for the underexplored territory between puree and soup. In the bowl, I garnished simply with a few drops of toasted sesame oil and a grating of nutmeg. The taste wasn’t as distinct from my usual squash soup as the carrot one was – maybe because I usually roast squash for soup anyway, which would also caramelize the sugars – but it still had a deep, hearty squash flavour.
But my favourite thing about these soups has been their texture: they’ve been the smoothest soups I’ve ever made, the easiest to strain and the most refined. I assume there’s something about pressure cooking the vegetables that breaks down the cells more completely than is possible at atmospheric pressure. (Or else I just haven’t been cooking my vegetables long enough!) And since there’s little to no water added, the purity of flavour is exquisite, and the final texture fully in your control. This technique now has me eager to make a full-on puree: I figure it should work with nearly anything but green vegetables, which would probably discolour.
I love the color of this soup…beautiful.
Matthew, now I feel terrible!! I added water to my pumpkin in the pressure cooker because I had juiced it first! I just looked at my comment and now I realize I left that out. I’m guessing that why the caramelization wasn’t as strong as before. Sorry for being a doofus.
In other news, I did two batches with carrot this week myself and got a noticeably less caramelized taste using my electric cuisinart on “low” – which Dave Arnold estimated to equate to 6 PSI. Personally, I kind of preferred the less caramel-flavored version.
Not to worry, Kevin! I’ve heard of lots of people adding a bit of water even to the original carrot soup, so it seemed like a reasonable safeguard. And there was still enough caramelization to make it interesting. If I’m feeling brave, I may try it again without the water.
I love this recipe and, like you, have tried it in various forms. My current favourite is to add leek and fennel to carrots (a medium leek and 2 small fennel to 1kg carrots), then blend in some caraway seeds with the butter.
Next up will be parsnips I think…
Fennel, in particular, sounds like a nice addition. Let me know how the parsnip goes! I’ve been meaning to try it, as well as beet. I was at a talk with Nathan Myhrvold recently, and he mentioned squash and beet work well.
Tried the parsnip version last night – spiced it with some ground cumin and coriander. It was excellent, a bit over creamy when made with the quantities of butter in the carrot recipe so I let it down with some frozen Momofuku Ramen broth I had leftover. Worked brilliantly.
I used about a kilo of parnsips, one medium onion and a leek, then some milk and water instead of veg juice.
The parsnips caramelised a lot more than the carrots have after a similar time, I think I’ll try it with less bicarb next time.