There are numerous approaches to making chan chan yaki, a Japanese dish of salmon and vegetables flavored with miso and butter. The dish originates in Hokkaido, but we learned the version that inspired this recipe at Kermis, a stamp-sized restaurant in Tokyo. Chef-owners Yasunobu and Yuko Namiki enclosed salmon fillets, vegetables and a few seasonings, including miso, in foil, then baked the packets. Once out of the oven, the fish and veggies were dotted with butter and allowed to rest until a brothy, rich sauce pooled in each packet. We use two types of mushrooms: meaty shiitakes and bouncy beech mushrooms. If you can’t find beech mushrooms—they’re sometimes sold in 3½-ounce packages and might be labeled “hon shimeji”—simply up the shiitakes to 12 ounces. The salmon, vegetables and sauce in each foil packet are transferred to individual bowls for serving.