Since it is impossible to pour hot soup into a raw piece of dough, there had to be a trick to making these soup filled buns. The secret is to turn the soup into aspic—a meat jelly. Many of the “quick” recipes call for using powdered gelatin. The more traditional recipes call for boiling pig skin for hours to break down its collagen to make the gelatin. If you are using this technique, it is advisable to begin making the soup the day before you plan to make these dumplings.
The simplest XLB soup recipes, I found, called for simply boiling the skin with some green onions and ginger. This type of recipe depends mostly upon the ingredients in the filling to give the soup most of its flavor. While there is nothing inherently wrong with this, I wanted something more.
Note: A couple of the recipes called for blending the skin into a slurry and either leaving it in or straining the broth after blending. I do not recommend doing this.
Other recipes use pork belly—with the skin still on—or a combination of pork cuts, including pig’s feet. These recipes produce a soup with an enhanced pork flavor and would still pick up some additional flavoring from the savory liquid shed by the filling ingredients. While better than the simplest recipes, the soup would still be fairly one dimensional.
The most savory soups included chicken bones and Chinese ham—as well as the pig skin. This technique produces a more complex flavorful broth. Some recipes take it a step further adding further flavor enhancers like: shitaki mushrooms, xaio xing, white pepper, and even fish sauce.
Chinese cured ham is very salty and and dry. Since it is cured raw you should always cook it very well before consuming. Smithfield country ham is an expensive substitute. Although several sites said that it is illegal to import it to the US, one of my local Chinese markets carried it. In Chinese recipes, it is usually used as a flavoring, rather than the main meat in a dish.
Karl’s Xiao Long Bao (The Soup)
½ lb. pork skin
1 lb. chicken skin and bones
2 oz. Chinese cured ham
4 cups water
2 green onions
1½ in. piece of ginger
1 cloves garlic, smashed
2 Tbs. soy sauce
2 Tbs. xaio xing rice wine
White pepper, ground, to taste
Kosher salt, to taste
1. Fill a medium pot with water and bring it to a boil.
2. Put the pig skin in the pot and boil it vigorously for 5 minutes.
3. Put the chicken pieces on a lipped baking sheet and broil the skin and bones until well browned on all sides.
Tip: Flip the pieces frequently, so that you do not burn any of the chicken bits.
4. Remove the pig skin and let it cool and scrub away any scum.
Tip: Dump out the water and scrub the pot, before using it again.
5. Cut all of the fat from the skin.
Tip: The first boil will have softened the half an inch of dense fat on the inside surface of the pig skin, making it easier to remove. If there is any meat on the fatty side of the skin, trim it free and return it to the pot.
Note: The skin will be about ⅜ of an inch thick after your remove the fat.
6. Return the skin to the pot, add the chicken scraps and Chinese ham.
7. Add 4 cups of water to the pot.
8. Cut the green onions into three parts and smash them with the flat of a clever.
Tip: Breaking the cell walls of the onions frees the juices.
9. Cut the knob of ginger in half lengthwise and smash the pieces with the clever.
Tip: Laying the semicircle of ginger with the cut side down and curved side up prevents it from sliding around as you smash the root.
10. Add the green onions, ginger, garlic, soy sauce and wine to the pot.
11. Bring the pot to a boil, cover, and reduce the heat.
12. Simmer the soup for 30 minutes.
13. Remove the pig skin from the pot and slice it into small strips.
Tip: When the skin it raw it is very hard to slice it into small pieces. After it has cooked for a while it become much softer.
Note: You are trying to extract as much collagen/gelatin as you can from the skin. The more surface area that is exposed the faster you can free it.
14. Return the skin to the pot and continue simmering the soup for another 3 hours.
15. Strain the solids from the broth and season with pepper and salt to taste.
Tip: You should be left with about two cups of soup at this point.
Note: If you used fatty pork or chicken skin de-fat the broth—by letting the fat rise to top and then blot it up with some paper towels. A little fat is flavor, but you do not want greasy dumplings. Also, if you wish, you may recover and mince the Chinese ham very finely to add to the dumpling filling.
16. Pour the soup into a shallow pan and cover it with plastic wrap.
17. Refrigerate the soup until it has fully set, at least two hours.
Tip: Over night is better.
18. Cut the aspic into small pieces—about ¼ inch dice—and remove it from the pan.
Tip: Cover and refrigerate the soup until you are ready to add it to the filling.