Heat the water and sake in a frying pan. Once it comes to a boil, reduce to medium heat. Defrost the flounder and wipe off any moisture before adding to the frying pan. Simmer for about 3 minutes over low heat, while ladling the sauce over the fish.
Add the sugar and ginger. Simmer for another 2 minutes, then add the soy sauce. Continue ladling the sauce over the fish for 2 minutes, then add the mirin. Once the fish has a glossy finish, it's done.
Serve up using a spatula.
Story Behind this Recipe
I had some inexpensive flounder in the freezer, so I simmered it. I usually make this without measuring but this time I measured while cooking.
Cooking fish with soft flesh in water and sake helps the proteins prevent the fish from falling apart since it sets the protein (collagen). It's a bit troublesome, but be sure to add the seasonings separately! The fish will absorb the flavours more once it cools, so take into consideration the time to cool and reheat time when preparing.