Depending on your culinary persuasions, you may find this piece on xiao long bao (Shanghai soup dumplings) to be overkill or just the type of deep examination this Chinese small dish deserves. As an aficionado of xiao long bao from an early age, I consider this a useful addition to the culinary literature. The piece culminates in the Shanghai Soup Dumpling Index which “applies a quantitative framework to the existing qualitative descriptors of the Shanghai soup dumpling.” If one of you readers is in Shanghai and can pick me up a printed copy, ping me!

Four measurements were collected: the weight of the intact dumpling (g); the weight of the soup (g); the weight of the filling (g); and the thickness of the skin (mm). This data was then calculated with the formula [(Filling + Soup / Thickness of Skin) x100] to assign a score representing the quality of structural engineering, the major challenge in the construction of a xiao long bao that meets the colloquial standards.

An analysis of the results combined with directly observed sensory research found xiao long bao with a score of 12.00 or above to demonstrate successful engineering. From a sensory perspective, these samples showed only minor variations, and were classified as Class A. Xiao long bao below this threshold but above a score of 6.75 showed satisfactory engineering and were judged Class B.

Author Christopher St. Cavish gives a great overview of just what a xiao long bao is and isn't, and what common variants should be called.

A soup dumpling is basically a balance between two competing forces: a thin-as-possible skin (whose purpose is to transport a meatball and soup, and then get out of the way) and as much filling as possible. There is a debate here as well, over the thickness of the skin, and whether a thicker wrapper represents a lack of technical faculty or a theoretical position on the balance of wheat flavor a dumpling should achieve. I subscribe to the former school of thought. There is no shortage of thick-skinned dumplings in China, filled with pork, even with soup; if you want one like that, don’t eat a xiao long bao. The elegance of a soup dumpling is its poise, the narrow margin that a cook must master to overcome the physics of a hot, wet package that wants to break. Soup dumplings are feminine. Sheng jian bao, a doughy, leavened dumpling that’s tough enough to survive a pan-fry and retain its pork and soup, are masculine. They are built of different stuff.

The Shanghai Soup Dumpling Index started with an ulterior motive: as a defense of Taiwanese chain Din Tai Fung. This is another fraught issue in Shanghai that must be addressed up front: the contest between Shanghai’s homegrown Jia Jia Tang Bao (Shop #35; Class A) and Din Tai Fung (Shop #14; Class A), a corporate raider from Taiwan. There wasn’t a clear answer when I started, and I haven’t found once since, but I set out thinking I’d collect a bit of hard proof about skin thickness.

Din Tai Fung has a cult following in the United States, but it's become a bit overrated there perhaps because it's actually so hard to find a well-made xiao long bao in most U.S. cities. I've been to the Seattle and Arcadia Din Tai Fung outlets, and they're solid but not spectacular. Really good specimens can be found in other restaurants in New York and in the Eastern parts of Los Angeles, but I've been disappointed, thus far, in San Francisco's offerings. Most have skin that tears too easily, or the flavor isn't the perfect mix of just a bit sweet pork, or there is no soup whatsoever, or the skin is too thick, or some combination thereof.

The outlets in Taipei, including the original, however...they dabble in some real sorcery, because they achieve an impossibly thin skin, just the right amount of soup, and a clean and delicate pork flavor. The thickness of the skin of a xiao long bao matters a great deal, just as the ratio of bun to meat in a hamburger matters. No one wants to eat too much dough relative to the meat and soup, and the impossibly thin skin of Din Tai Fung's achieves, to my mind, an ideal ratio of skin to filling.

I happen to be in Taiwan now, and just this morning I had ten of Din Tai Fung's pork xiao long bao (that's the original recipe and still the best; leave all those truffle and crab and other gimmicky variants for the barbarians). All ten of them had a uniformly thin skin, and not a single one broke as I picked them up with my chopsticks and dipped them in the ginger-vinegar-soy sauce and transferred them to the soup spoon. Not that they should tear open if wrapped properly, but the fact that they didn't still felt like a miracle.

As with many Taiwanese restaurants, the chefs wrapping the xiao long bao worked in a glass-encased kitchen so diners could observe them in action. Each wore a surgical hat and mask and full length aprons or scrubs, all in resplendent white, rendering them visually less as chefs than chemists conducting research with combustible chemicals. Combined with the organized workspaces in the open kitchens, the sensation of watching them was one of cleanliness, delicacy, and precision. My friend, a local, told me it's a coveted position to wrap xiao long bao at Din Tai Fung in Taipei, and that they try to screen for tall, good-looking candidates.

A Din Tai Fung outlet is coming to San Jose. It will be massive at 8,500 square feet with 200 seats, and still you should expect to wait in long lines after it opens, no matter the hour.