Why It Works
- Freezing and thawing firm tofu removes excess water and alters its structure, turning it into a sponge that soaks up all the flavors of the broth.
- A mixture of chicken powder, water, and chicken stock makes a light-bodied broth that's easy to bring together in minutes.
Many households in Northeast China use the long, bitter winters to their advantage by storing ingredients outdoors. Since the temperatures are well below freezing, everything kept outside freezes solid. This is great news in terms of the preservation of ingredients that would have otherwise gone bad, but it’s also great news for texture and flavor—as evidenced by this warming tofu, cabbage, and pork soup.
In the case of the tofu, as it freezes, the water inside of the tofu crystallizes as ice, which expands and pushes apart the proteins that give the tofu its structure. When these ice crystals then melt and the water drains away, they leave behind large holes in the tofu, giving it a chewier, spongier texture. This frozen-then-thawed tofu can then be pressed to drive off more water for dry heat applications, such as grilling, where it'll pick up more flavor and caramelize better without all that excess moisture in the way.
Where this frozen tofu really shines, however, is in braises, soups, and sauces. The now-opened lattice of the defrosted tofu makes it not only sponge-like in appearance, but also sponge-like in performance: those air pockets left behind by the ice crystals transform the tofu into a highly absorbent ingredient, meaning it will soak up any liquid it’s cooked in. The result is meatlike, chewy, juicy, and very flavorful—even when cooked in something like this recipe's very basic broth, which consists of pork, cabbage, chicken stock, garlic, and ginger.
All tofu can be frozen to achieve a similar effect, but based on my tests, the best results come from freezing whole blocks of firm tofu. Firm tofu has a higher protein content and lower water content than silken tofu, which means that it also has the strongest lattice structure, and it will consequently hold together better after it's thawed. Using whole blocks as opposed to slices or cubes of tofu also seems to yield larger air pockets, possibly because whole blocks retain more moisture. That said, there are advantages to freezing sliced tofu, which is how most Northeast Chinese families do it. What you lose in air pocket size you gain in convenience: sliced frozen tofu can be dropped right into a simmering pot, rather than having to fully thaw a block of tofu and then slicing it before adding it to the pot.
- 1 pound (450g) firm tofu, drained of packing liquid
- 17 1/2 ounces (500g) Napa cabbage, from about half a 2 3/4-pound head
- 2 tablespoons (30g) neutral oil
- 1 1/2-inch knob fresh ginger (3/4 ounce; 20g), peeled and thinly sliced
- 4 medium cloves garlic (25g), smashed
- 5 1/2 ounces (155g) very thinly sliced boneless, skinless pork belly or pork shoulder (see note)
- 1 tablespoon (15g) light soy sauce
- 2 cups (475g) homemade chicken stock or low-sodium, store-bought broth
- 2 cups (475g) water
- 1 tablespoon (10g) Diamond Crystal kosher salt; for table salt use half as much by volume or the same weight
- 2 teaspoons (10g) chicken bouillon
- 1/4 pound (115g) dry rice noodles, soaked in room temperature water for 5 minutes, then drained (see note)
- Cooked long-grain white rice, for serving
Place tofu in a sealed container or on a tray wrapped with plastic and freeze for at least 3 hours and up to 6 months. When fully frozen, the tofu will turn a darker shade of yellow/brown and become slightly translucent.
When ready to cook, fully thaw the tofu, at least 3 hours at room temperature or 8 hours in the fridge. Gently squeeze the tofu between your palms to express as much water as possible without damaging it. Cut tofu into 10 equally sized pieces.
Core the Napa cabbage and separate the leaves. Cut the tender portions from the thicker stem of each Napa cabbage leaf. Tear tender portions into roughly 2-inch pieces, and cut thick stems into roughly 5-inch by 1-inch strips. Keep separate and set aside.
In a large Dutch oven, heat oil over medium-high heat until lightly smoking. Add ginger and saute until lightly browned around edges, about 30 seconds. Add garlic and cook until lightly browned, about 15 seconds. Add sliced pork and cook, stirring, until last traces of pink are gone, about 30 seconds.
Add sliced Napa cabbage stems and cook, stirring, until they begin to soften, about 30 seconds. Stir in soy sauce and cook until mostly dry, about 30 seconds. Add the torn cabbage leaves, followed by the chicken stock and water. Bring to a boil.
Add the tofu to the pot along with the salt and chicken bouillon. Return to a boil, cover, and let simmer until the Napa cabbage stems have softened, about 5 minutes.
Season with salt, if necessary. Add soaked rice noodles, and let simmer until the rice noodles are soft and cooked through, about 2 minutes (note that cooking time will depend on the type of rice noodle you use). Serve warm with white rice.
You can find very thinly sliced pork belly and shoulder at many Asian markets.
There are many types of rice noodles, any of which will work here. I prefer a Chinese rice vermicelli in this recipe, though many Northeast Chinese homes prefer chewier cellophane noodles.
Make-Ahead and Storage
The tofu can be kept in the freezer for up to 6 months, then defrosted as needed.