Thinly slice the onion. Blanch the spinach, squeeze out the water, and cut into 3 cm pieces. Shred the shimeji mushrooms into small clumps.
Combine the ingredients for the soy milk and white miso sauce in the order they're listed using a whisk.
Put the oysters into lightly salted water (not listed). Shake them to wash, and drain in a colander.
Bring the sake to a boil in a small pot, add Step 3, and cover with a lid. After a minute or so, once the oysters have plumped up, turn off the heat, and drain. Separate the oyster meat and the broth, and set aside.
Heat the ● oil and butter in a frying pan, and stir-fry the onion and shimeji mushrooms. When the onion has become translucent, add the oyster broth you set aside in Step 4.
When most of the broth has evaporated, add the soy milk sauce from Step 2 and mix. As soon as the sauce thickens, turn off the heat.
Lightly coat heat resistant dishes with butter (not listed), evenly place the oysters from Step 4 and spinach from Step 1 in each dish, and evenly pour over the sauce from Step 6.
Scatter the pizza cheese on top, and sprinkle with panko and grated cheese. Bake in the toaster oven.
When it's nicely browned on top, it's done. Sprinkle on chopped parsley and enjoy while it's piping hot.
It's also delicious with salmon. Remove the skin from the salmon, and cut diagonally into bite-sized pieces. Sprinkle 1/4 teaspoon of salt, and pepper, and rub into the salmon pieces. Lightly coat the salmon in rice flour.
Heat olive oil in a frying pan, and add the salmon. Brown both sides and take them out on a plate. (I used 2 fillets of salmon and their net weight was about 180 g.)
Heat the ● olive oil and butter in the same frying pan, and sauté the onion and shimeji mushrooms.
When the onion has become translucent, add the soy milk sauce from Step 2. Turn off the heat as soon as the sauce thickens.
Same as Step 7, place the salmon and spinach in heat resistant dishes. Pour over the sauce from Step 13, sprinkle with cheese and panko, and bake in the toaster oven until brown.
Enjoy while piping hot!
Story Behind this Recipe
This gratin with Japanese sauce is a family favorite. Miso and cheese are both fermented foods, and they go really well together. I like adding soy milk to this sauce, instead of milk. I thought about the nutrients that are beneficial for the body during winter, like iron, for instance, which strengthens the immune system. And that's how I came up with this recipe.
Cook the oysters thoroughly in Step 4 to prevent them from being undercooked.
I removed the skin from the salmon for children, but you can cook it with the skin still on.
The sauce made with rice flour doesn't form lumps, so you can make this sauce without fail.