- 1/2 cup apple cider vinegar
- 2 Tbsp light brown sugar
- 2 tsp salt
- 2 tsp ground mustard
- 1/2 cup water
- 1 hothouse cucumber, cut into 1/4" pieces
- 1/3 cup finely chopped red onion
- 1/3 cup golden raisins
- 2 tsp mustard seeds
- 1 lb skin-on white fish, such as halibut or Chilean sea bass
- 3/4 cup white miso
- 3 Tbsp mirin
- 3 Tbsp sake
To make the relish, in a saucepan over high heat, bring vinegar, brown sugar, salt, ground mustard, and water to a boil, stirring occasionally, until sugar and salt dissolve, about 5 minutes.
In a heatproof, resealable container, add cucumber, onion, raisins, and mustard seeds. Pour hot brining liquid over cucumber mixture and stir to combine. Let cool to room temperature, then cover and chill at least 2 hours before serving.
To make the fish, evenly slice fish into 4 pieces and season with salt.
In a small bowl, combine miso, mirin, and sake. Pour half of miso mixture in a 13”x9” baking dish. Arrange fish in a single layer. Top with remaining miso mixture. Cover and refrigerate overnight.
Preheat broiler. Transfer fish to a rimmed baking sheet, discarding miso mixture. Broil fish until golden brown around edges, about 7 minutes. Reduce temperature to 450° and cook to an internal temperature of 140°, about 6 minutes. Serve with drained relish.