Ingredients
1 (750 mL) bottle sake, preferably Junmai Daiginjo
1 tablespoon plus 1 teaspoon mirin
1 1/2 teaspoons yuzu kosho
1 1/4 cups (2 1/2 sticks) unsalted butter
Coarse salt
Zest of 2 yuzu or limes
Yuzu juice
2 tablespoons extra-virgin olive oil, plus more for baking sheet
4 (5-ounce) pieces skinless wild striped bass
Maldon sea salt
Freshly ground espelette pepper
4 sprigs fresh thyme
2 cloves garlic, peeled
2 bunches spinach, preferably Bloomsdale spinach
Freshly grated yuzu zest, optional
Preparation
Place sake and mirin in a nonreactive saucepan over medium-high heat; cook until reduced by two thirds. Remove from heat and add yuzu kosho. Using an immersion blender, blend to combine. Cut 1 cup (2 sticks) butter into small cubes and add to saucepan. Using the immersion blender, blend to combine. Season with salt, zest of 1 yuzu, and a few drops of yuzu juice; keep warm and set aside.
Heat 1 tablespoon butter and 2 tablespoons olive oil in a large nonstick skillet over medium heat. Season fish on both sides with Maldon sea salt and espelette pepper. When butter has melted, add fish to skillet, skin-side down; reduce heat to low and cook, basting with butter and olive oil from skillet, 3 to 4 minutes. Turn and add thyme and one garlic clove to skillet; cook, continuing to baste, until fish is cooked through, about 3 minutes more. Remove fish from skillet and transfer to a small lightly oiled baking sheet; let stand in a warm place for 10 minutes. Preheat broiler.
Wipe skillet clean with a clean paper towel. Add remaining tablespoon butter and 2 tablespoons olive oil and heat over medium heat. Insert the tines of a fork into remaining clove of garlic and set aside. Add spinach to skillet and season with salt; cook, stirring with garlic clove attached to fork, until spinach is wilted.
Transfer spinach to a paper-towel-lined plate. Gently reheat fish under a broiler until just heated through. Divide spinach evenly among 4 warmed plates and top each with a piece of fish.
Strain sauce; using an immersion blender, briefly blend sauce to reincorporate. Spoon sauce around fish and top with yuzu zest, if using; serve immediately.
