Preheat a wok and heat the oil in it. Fry thinly sliced ginger, thinly sliced chicken, thinly sliced oyster mushrooms and finely chopped garlic in hot oil. The result should be a state of chicken and mushrooms in which they could already be eaten without further cooking. The mushrooms need time to start releasing the juice. The juice must have time to evaporate under high temperatures, and oyster mushrooms must get a pleasant brown crust and fill the entire kitchen with the annoying aroma of freshly fried mushrooms.
At this point, add the soy sauce, star anise, finely chopped peppers and chilli peppers, cut into thin rings, stir, simmer for a minute and pour in chicken broth. Boil the soup for five minutes.
During this time, cook the udon noodles in salted water in a suitable saucepan.
Remove the soup from the heat, squeeze in lemon juice, toss onion stalks, udon noodles, stir and serve.