Marinating fish in miso is a time-tested Japanese technique that is surprisingly simple: Miso is combined with sugar, sake, and mirin to make a marinade that is typically applied to oily fish for a few days; during that time, the marinade seasons the fish and draws moisture out of its flesh so that it becomes quite firm and dense. The fish is then scraped clean and broiled, producing meaty-textured, well-seasoned fillets with a lacquered savory-sweet glaze. Those flavors pair particularly well with a rich fish like salmon, and the marinade takes minutes to make. But we were determined to find a way to minimize the preserving time and get this dish on the table as quickly as possible.