Add the sake and water to a frying pan and bring to a boil. Reduce to low heat, add the cod after patting it dry with a paper towel, and simmer for about 2 minutes while spooning the broth over the fish.

Add the sugar and ginger, and simmer for about 2 minutes.

Add the soy sauce and mirin, and simmer for about 3 minutes before turning off the heat. Before serving, warm it up and add the soy sauce for a quick simmer. Use a spatula to plate!