Dissolve 1/2 teaspoon salt in 2 cups hot water, and add tofu. Soak 5 minutes, then drain.
Heat wok over high heat until a bead of water dropped onto cooking surface evaporates immediately. Add oil, swirling wok to coat, and heat until it begins to smoke. Add beef and stir-fry, breaking up lumps, until no longer pink, about 2 minutes. Stir in wine and 1/2 teaspoon soy sauce and stir-fry 30 seconds.
Add chile bean sauce and stir-fry until fragrant, about 15 seconds. Add ginger, chile powder, and black beans and stir-fry until fragrant, about 30 seconds. Add broth, remaining 1/2 teaspoon soy sauce, and tofu, then reduce heat and simmer, stirring gently, about 2 minutes.
Add leeks and simmer, stirring occasionally, until just tender, 2 to 3 minutes. Stir potato starch mixture and add to tofu, then cook, stirring, until sauce is thickened, about 1 minute.
This serves two people as a the main dish, or up to 10 people as part of a family-style meal with a variety of dishes.