- 1 cup water
- 6 tablespoons reduced-sodium soy sauce
- 2 tablespoons mirin (Japanese sweet rice wine)
- 1/8 teaspoon ground sansho pepper (sometimes labeled “sansyo”), plus additional for sprinkling, or 1 teaspoon whole Sichuan peppercorns
- 1 shallot, sliced
- 3 garlic cloves, thinly sliced, divided
- 2 teaspoons vegetable oil
- 7 ounces fresh enoki mushrooms, cut into 3-inch lengths and spongy base discarded
- 5 ounces fresh shimeji mushrooms (sometimes called beech mushrooms), spongy base discarded
- 6 (6-ounce) pieces black cod fillet with skin
- 1 teaspoon vegetable oil
- thinly sliced scallion greens
- Bring water, soy sauce, mirin, sansho pepper, shallot, and one third of garlic to a boil in a 1- to 2-quart heavy saucepan, then simmer 5 minutes. Let broth stand off heat 10 minutes.
- Cook remaining garlic in oil in a 10-inch heavy skillet over medium heat, stirring, until just golden. Add all mushrooms and cook, stirring occasionally, until tender, about 3 minutes.
- Strain broth through a fine-mesh sieve into mushroom mixture, discarding solids, and simmer 1 minute.
- Pat fish dry and sprinkle with 1/2 teaspoon salt and 1/4 teaspoon pepper. Heat oil in a 12-inch heavy nonstick skillet over medium-high heat until hot, then sauté fish, skin side down, turning once, until golden brown, just starting to flake, and just cooked through, about 10 minutes.
- Transfer fish to shallow bowls. Reheat broth and divide among bowls, then sprinkle very lightly with more sansho pepper (if using).