Take your fillets and sprinkle on a light dusting of salt. Make sure they’re evenly covered and leave to stand for 30 minutes. Dab with kitchen towel to wipe off the salt and remove any excess water.
In a bowl, mix together the sake, mirin and white miso. Evenly spread approximately 1/2 of the miso mixture onto a large piece of cling film. Place the fish fillets onto the cling film, then spoon on the rest of the miso. Sandwich the two pieces together, wrapping the cling film around them. Gently massage the miso, making sure that it covers all of the fish. Leave the fish to marinate for 2-3 days in the fridge.
30 minutes before you want to cook your fish, remove it from the fridge. Gently scrape your marinade off the fish; this is important as any leftover miso may burn when you cook it.
Pre-heat your oven to around 200°C. Place the fish on baking paper or a non-stick pan and cook for 10-15 minutes. Garnish with a little bit of pickled ginger and serve.
• If you don’t want to eat your fish straight away, you can freeze the fillets after they have marinated and cook them when you’re ready.
• You don’t have to use black cod for this recipe, any white fish or salmon will be equally delicious.