Ok, so we've been through guo tie (fried dumplings), the thick-skinned, crisp-on-the-bottom potstickers from Beijing, but what about their Shanghai counterparts? I'm talking the delicate xiao long bao of Shanghai; the ones that appear to be your standard dumplings, but miraculously burst open in a mouthful of savory broth with a tender meatball floating inside as you bite into them.
They're not extremely tough to make, but they are time-consuming, and here's why: in order to get the broth inside the 'pling, it must first be solidified, and that means making a real chicken and/or pork broth—no cheating by using the canned stuff.
When you cook down real chicken or pork bones, the connective tissue collagen (mainly from in and around the ligaments where the muscles connect to the bones and the joints) slowly breaks down into three gelatin molecules. It's these long, string-like proteins that form a connective matrix that adds viscosity to a well-made stock.
A slow-cooked broth made with plenty of bones and reduced a bit should gel into a firm, Jell-O-like texture when it's chilled, like the broth above.
Of course, if you're really desperate for a fix, you could always use packaged commercial gelatin (or even agar agar) to set canned chicken broth into a gel, but where's the fun in that?
After making your broth, the rest of the process is simple—no different from any other dumpling. Blend together your filling ingredients (I like to use a mix of pork and shrimp flavored simply with soy sauce, XioaShing wine, salt, sugar, and a few scallions), add your gelled broth, fold them into dumpling wrappers, and steam them.
"With soup dumplings in particular, shape is important."
This is one case where you must use homemade dough—store-bought dumpling wrappers are not stretchy enough, and you will not be able to fold them into the right shape. With soup dumplings in particular, shape is important. Rather than having a long seam running along one side (like with fried dumplings), soup dumplings are pleated up like a purse, so that the only place where filling could possibly leak out is the tiny hole at the tip.
The most hardcore soup-dumpling makers will add filling and gelled broth separately. I find this very difficult, so I just mix the gelled broth directly into the filling. The end result: the meat forms a slightly looser meatball inside the wrapper as it cooks because of all the space left behind from the melting broth, but to my taste, this is not a bad thing.
When steaming, you must line your steamer with something to prevent sticking. Parchment paper works, but napa cabbage leaves are cheaper, tastier, and more traditional.