Make the miso blend: Put the ● ingredients in a small cup, heat up in the microwave to about 60°C, and mix well.
Cut the onion into 5 mm thick slices. Shred the mushrooms up.
Wash the salmon quickly and pat dry with paper towels.
Cut a 40 cm or so length of aluminium foil and layer the ingredients in this order: Bean sprouts, onion, salmon (seasoned with salt and pepper), and finally the mushrooms.
Sprinkle on 1 teaspoon of sake. Put a generous amount (1 heaping tablespoon) of miso on, and top with the cheese.
Gather the foil over the contents and fold close. Leave plenty of space in the packet. Tightly seal the ends of the foil too.
Put the foil packet in a frying pan. Turn the heat on to medium, and cook for 3 minutes. Turn down the heat to low and cook for another 5 minutes, then turn off the heat and leave to rest for 2 minutes to steam-cook the contents of the foil packet.
It's piping hot, so wait for 30 seconds after removing the lid from the pan before taking the packet out. Be very careful when opening the packet!
You can also make this in a frying pan without wrapping it. If using a non-stick pan just layer the ingredients in as-is; or, line the pan with heatproof kitchen paper first.
Layer and season the ingredients in the same way as the foil packet. Put the miso and cheese in the middle. Steam-cook with a lid on as described in step 6.
The cheese has melted and mixed with the miso to make a creamy sauce.
Serve with the sauce.
Story Behind this Recipe
In the Sanuki region (in Kagawa prefecture) miso is a must in oden (fish cake stew)! When I had some miso left over from making oden, I tried adding it to foil-wrapped salmon, and the result was surprisingly creamy and delicious. Since then it's become a firm family favorite! It's also delicious if you add some ground sesame seeds to the miso.
You can use melting or non-melting type sliced cheese. The non-melting type has a stronger flavor, which I prefer. It will still melt though. You don't need to oil the foil or the frying pan. The mixed miso will be sweeter with white miso, but if you don't have it just use the miso you have on hand and adjust the sweetness with sugar.