Mushroom and Egg Donburi

There are many different types of donburi, a Japanese rice bowl topped with some combination of meat and vegetables, including gyudon (beef), katsudon (pork) and oyakodon (chicken and egg). In this meat-free version, which was inspired by oyakodon, mushrooms and leeks simmer in a dashi-based sauce before beaten eggs are poured over and cooked until custardy. The combination of mushrooms and leeks is especially satisfying because it doubles down on the savory and sweet contrast in the sauce, but vegetarian versions of oyakodon are also frequently made with cubed tofu or other thinly sliced vegetables and egg. To keep it vegetarian, use fish-free dashi, which can be purchased or made with dried shiitakes and kombu. (You can add the rehydrated shiitakes to the mushroom mixture.)