Parboiled shiitake and broccoli florets are tossed in soy garlic sauce thickened with potato starch. The addition of mirin makes this side dish subtly sweet.
Boil four cups of water in a wok with two pinches of salt and half a teaspoon of sesame seed oil.
Drop in the broccoli florets, stir and boil for a minute. Scoop out and dump into a bowl of icy water.
In the remaining water, boil the shiitake slices for a minute. Scoop out and add to the broccoli in the icy water.
Drain the broccoli and shiitake and spread on a rack or a kitchen towel.
Rinse and wipe the wok, pour in the cooking oil and heat.
Saute the garlic and onion just until softened.
Mix together the soy sauce, mirin, black pepper, vegetable broth, remaining sesame seed oil and starch. Pour the mixed sauce over the garlic and onion, stir and leave to boil.
Lower the heat, stir once more, and cook for a minute.
Add the shiitake and broccoli. Toss until heated through.
Taste, adjust the seasonings, if needed.
Optionally, sprinkle with chili flakes before serving.