Black Cod w/ Mushrooms & Sansho Pepper

Serves: 6 / Active time: 15 minutes/ Start to finish: 30 minutes

FOR BROTH
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 oz fresh enoki mushrooms, cut into 3-inch lengths and spongy base discarded
5 oz fresh shimeji mushrooms (sometimes called beech mushrooms), spongy base discarded

FOR FISH
6 (6-oz) pieces black cod fillet with skin
1 teaspoon vegetable oil
Garnish: thinly sliced scallion greens

MAKE BROTH:
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.

SAUTÉ FISH:
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).

Note: Broth can be made 1 day ahead and chilled, covered (once cool). Gently reheat before using.