Mix the sugar into the mirin and sake and stir well till dissolved
Stir through the miso, garlic and ginger
Place the fish in a tupperware container and pour over the glaze, turning the fish to ensure it is fully coated
Place in the fridge for at least 2 hours or longer if possible. You should be able to marinade the fish for 24 hours if it is fresh enough
Remove from the fridge about an hour before you want to cook and bring to room temperature
heat your oven to 220C. Take the fish portions out of the marinade, keeping as much of the glaze as possible
Heat a non-stick, skillet or frying pan and cook the fish for 1 minute, service side down.
Turn the fish and place the pan in the oven for 6-10 minutes, depending on the thickness of the portions, until it is cooked, the edges are nicely caramelised from the glaze and the fish is opaque
Serve with rice, steamed or stir-fried green vegetables and lime