Pat the chicken dry with paper towels.
Heat the cooking oil in a frying pan.
Sear the chicken over high heat until browned. Flip over for even browning.
Scoop out the half-cooked chicken and set aside.
Pour off the cooking oil (you'll need some of it later).
Pour the soy sauce and Sriracha into the pan. Add a quarter cup of the water in which the mushrooms were soaked (or plain water if using fresh shiitake). Add the ginger and garlic. Stir.
Put the chicken back into the pan with the sauce. Simmer for 30 to 35 minutes. Turn them once or twice during cooking.
About ten minutes before the chicken is done, prepare the shiitake mushrooms.
Take two tablespoonfuls of the oil in which the chicken was browned and pour into a small frying pan.
Heat the oil. Add the sliced shiitake mushrooms. Sprinkle with a little salt and pepper. Cook over medium heat, stirring occasionally, for three to four minutes. Stir in the scallions. Cook for another 30 seconds. Turn off the heat but leave the mushrooms in the pan. The sides touching the pan will brown to a light crisp in the residual heat. It's a lovely texture.
The soy-braised chicken with shiitake mushrooms is lovely to serve with rice. Ladle rice on a plate. Place a piece of chicken on top. Spoon some of the shiitake on the side. Stir the lemon juice into the remaining braising sauce and drizzle over the chicken and mushrooms.