The Food Lab: This is How Hot and Sour Soup Should Taste
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Last week, Ed came into the office excitedly exclaiming that he'd just had "the first hot and sour soup that has any sort of complexity," made by Joe Ng of RedFarm. As a hot and sour soup lover, this actually came as no surprise.
Listen: Hot and sour soup and I have the kind of relationship that they make movies about. Movies of the kind my wife enjoys watching on plane rides, with fine, soft-spoken British actors and plots that chronicle tender, life-long relationships.
We first met in the flesh at a roadside Chinese restaurant in New Jersey when I was six years old. Sure, I'd caught glimpses of her in the past, inhaled her heady aroma as she was whisked by on the arm of a waiter. She'd had a previous engagement with the charlatan at table 12, see, but I was intoxicated by her delicate spicy perfume nonetheless.
I'd been working up the courage for years to ask for her, afraid that if I turned my back on the precious wonton soup that I'd loved since before I could remember, that I'd risk losing both of them and I'd be stuck like a sucker sipping on egg drop forever.
I must say: it wasn't love at first sip. Slick and thick with cornstarch, the stuff I was served was tasty, but did not deliver the pungent spice and acidity that both the name and the aroma promised. Here's the fact: Most restaurant hot and sour soup stinks.
It wasn't until years later, when my parents blew the dust off their tattered and dog-eared copy of the Joyce Chen Cookbook and turned to the hot and sour soup recipe that I discovered what I'd been missing that whole time: freshly made hot and sour is an entirely different beast.
Why is that? It all comes down to the fact that at the vast majority of restaurants, the hot and sour soup is made in a large batch with little attention paid to detail. Worse, it then gets transferred to a steam tray where it steams away, reducing itself to a slick, goopy sludge. As it sits, the heat of the white pepper and the bright, sweet flavor of Chinkiang vinegar rapidly deteriorate. Even a few minutes can make a difference: in the time it took to set up and photograph the bowl of soup you see in this photo, it had already dulled, requiring a fresh splash of vinegar to punch it up.
Great hot and sour soup should be rich and thick, but never gloppy, the broth packed with flavor even before the vinegar and pepper get added. The vegetables—wood-ear mushroom and day lily stems—should be crunchy and bright; the slivers of tofu and pork, tender and comforting. Above all, the soup should taste fresh.
I've spent many years working on my recipe for hot and sour soup, based largely on the original recipe my parents followed. Here's how to make it, step-by-step.
Chinese broths fall into two broad categories. Many soups are made with simple bone and aromatic broths, but when you want to get really fancy, a refined broth is what you use. The king of refined Chinese broths? Superior stock, made with a combination of chicken, pork, and Jinhua-style smoked ham, a cured ham with a flavor not unlike country ham or prosciutto (either will work if you can't find Jinhua).
Now, some Chinese food experts may scoff at the use of a superior stock for a dish as simple as this, and to be fair, a simple chicken stock will work—even if it's store-bough—but if the best is what you're after, then just as with French cuisine, the flavor of the starting broth can have a profound impact on the finished product.
For my wonton soup recipe—a soup that has very few flavorings added to the broth before serving—I went with a combination of chicken bones, ham, and pork trotters to provide both flavor and body to the stock. With the hot and sour soup, that rich porkiness is not as essential—it gets largely suppressed by the aromatics later on.
Instead, here I use a mix of chicken carcasses and chicken feet, which provide plenty of rich gelatin, and do so much faster.
The aromatics are classic Chinese: scallions, onion, garlic, and ginger, added generously to the pot.
The other morning, Leandra walked into the kitchen and caught me in a rather compromising position with a chicken carcass and a cleaver. I didn't bother trying to explain it to her, but I'm happy to explain it to you guys.
Pro-tip: Hack your chicken carcasses to bits before making stock. Not only will it make you feel like a medieval viking-style badass, but it'll also make your broth come together much faster. The more finely you chop the bones, the more surface area they have, and the more channels for proteins, minerals, and other goodies to get extracted into the broth.
While it's not 100% essential (especially if you don't care much about the color of your final broth), I generally blanch my bones before simmering them. This blanching process—placing the bones in cold water, bringing it up to a boil, then dumping it out—will cause some of the most easily extractable proteins to coagulate so they can be washed away.
It just so happens that these early extractables—mainly blood and myoglobin trapped near broken bones and joints—are the ugliest looking and least flavorful bits you'll get out of the chicken. Washing them away gives you a cleaner, better tasting broth.
This step also saves you a bit of skimming down the line (you do skim your broth, right?!)
With a well-chopped carcass, you should have a rich, flavorful chicken broth in just about an hour. Plenty of time to pull together your other ingredients.
There are no real hard and fast rules when it comes to populating your hot and sour soup with chunks—Fuschia Dunlop has a particularly enticing-looking version made with lots of mushrooms in her book Every Grain of Rice—but I like to stick with the ingredients I grew up with, starting with black fungus (a.k.a. wood-ear) and day lily bulbs.
Both can be found sold dried at Asian markets and need to be re-hydrated—just soak them in separate bowls of water for about half an hour and they're ready to go.
Black fungus comes in several different grades that range in price. As far as I've been able to taste, the major difference is in their pre-treatment. The cheaper stuff needs to be trimmed of hard nubs and cores after soaking, while the more expensive packages come with already-cleaned fungi.
Extra-firm tofu of the cotton-y variety is rarely my tofu of choice, but it's ideal in this soup, where its network of fine pores absorbs the broth we've worked so hard to make flavorful.
Egg, incorporated in the style of egg drop soup might be an Americanized tradition, but that don't bother me none. I love the slippery little flowers the egg produces when you whisk it together with a touch of cornstarch and drizzle it into the hot soup.
Meat is definitely optional here, and more often than not, I'll go with a completely meat-free version, but if you want to stay true to upgraded-restaurant form, you'll want to include some pork shoulder, trimmed of fat and connective tissue and sliced into very fine slivers.
Some fresh aromatics are also essential. While the broth simmers, I slice up a bunch of scallion whites and greens, julienne some young ginger, and wash and pick some cilantro leaves, ready to be sprinkled on just before serving.
Other ingredients you can have on hand to add to the soup: sliced button mushrooms. Sliced fresh or dried (and soaked) shiitake mushrooms. Slivers of chicken. Fresh or canned bamboo shoots. And of course, [INSERT FAVORITE SOUP INGREDIENT HERE]. Get the idea?
To Fry or Not to Fry?
Most recipes for hot and sour soup require nothing more than adding your solid ingredients to the simmering stock, but Fuchsia Dunlop suggests stir-frying your mushrooms, day lily bulbs, and other aromatics to help develop some browned, seared aromas before adding your stock.
I tried this, comparing it side by side with a simply simmered batch and found the flavor impact to be almost undetectable once the soup was finished. I'm going to leave that step out from now on.
Hot, Sour, and Thick
Once your broth is finished cooking, has been strained and seasoned (I use a dash of soy sauce, some regular salt, and a drizzle of sesame oil), and your solid ingredients added and simmered for a few moments, there are two things left to do.
The first one is rather controversial: thickening. In certain Chinese traditions, hot and sour soup is thickened with blood from either a chicken or a pig. Not only is blood not easy to come by in the US, it's also not high on most folks' lists of "things I love to eat," including mine. Instead, hot and sour soup in the U.S. is more often than not thickened with cornstarch.
Some writers and eaters—probably those that have been scarred by years of eating the steam-table glop—insist on using no thickener at all. I personally like to use just a hair—enough to add some body to the soup and help the solid elements stay suspended, but not so much that it becomes mouth-coatingly slick. About 2 teaspoons of cornstarch per quart of soup is a good level.
The second and final step? Adding in the hot and sour elements. Depending on who you ask or what region of China your recipe stems from, the heat can come from either dried red chilies, or from white pepper. In the U.S., it's almost universally the latter.
For the sour, dark Chinkiang (a.k.a. Zhenjiang) vinegar made by fermenting black glutinous rice is key. It has a deep, almost smoky flavor with an aroma that's not unlike balsamic vinegar, but with none of balsamic's overt sweetness. If you can't find it, look a little harder! Still can't find it? Ok, a combination of red wine vinegar and apple cider vinegar will give you a pretty close approximation.
And this is key: Add in that pepper and vinegar right before serving. They lose aroma fast. In fact, for good measure, it's a wise idea to have a bit at the table so your guests can season their bowls as desired.
That fresh white pepper and vinegar hit? That's the difference between the hot and sour soup that's good enough to keep you satisfied in your own company at home, and the hot and sour soup that's so good you absolutely must take it home to meet the parents.
It's the hot and sour soup I fell in love with, but I'm not so selfish I wouldn't share it with you all.
About the author: J. Kenji Lopez-Alt is the Chief Creative Officer of Serious Eats where he likes to explore the science of home cooking in his weekly column The Food Lab. You can follow him at @thefoodlab on Twitter, or at The Food Lab on Facebook.