This is a rather easy to make and yet quite tasty dish. I had shimeji しめじmushroom (clam shell mushrooms) and about 1 lb of salmon fillet. I did not have the energy or time to make anything complicated so I made this dish. I did not follow any particular recipe but the combination of butter, sake and miso cannot go wrong.
Salmon fillets: I divided a 1lb fillet into two equal pieces (scales and pin bones removed).
Scallion: I cut on bias into 1-2 inch pieces. I used one scallion per packet.
Mushrooms: I used a combination of hon-shimeji (brown clamshell) and white clam shell mushrooms but any mushroom such as shiitake or enoki will also do. I just used whatever amount I had. I cut off the root end and quickly washed and drained it.
I took a large sheet of aluminum foil, greased it with sweet butter. Next came the sliced scallion and the salmon fillet skin side down. I placed thin pats of butter(1/2 tbs) and miso (1tbs) (#1 below) on the fillets and topped with the mushrooms (#2 below). I closed the packet by folding and crimping the edges together (#3) but just before I closed it completely, I added sake (3-4 tbs). I placed the packets into a pre-heated 400F toaster oven (convection) for 30 minutes. When I opened the pouch (#4), I discovered the miso had not dissolved but got baked and darkened. I simply removed the miso and dissolved it into the juice/sake accumulated in the bottom of the pouch.
I served this with baby bok choi (quartered) which was boiled in water with splash of sake and salt (The first picture). Since I cooked this ahead of time, it lost its green color. Although I did not use sugar or mirin, the sauce was sweet enough. The salmon had a poached-like consistency that was nicely tender. The baked miso, added a very nice nutty flavor and richness.