"My host-mother in Japan introduced me to this sweet sauce flavored with miso and mirin. Miso sauce can stay in the fridge for a pretty long time, so you can make a lot of it at once. Grilled tofu, fried eggplant, or pan-seared fish complement it well."
Combine mirin, miso paste, egg yolk, and sake in a saucepan and mix well; bring to a boil, stirring constantly. Reduce heat to low and simmer, stirring constantly, until sauce is the consistency of jam, 10 to 15 minutes.