In a bowl, combine ginger, Shaoxing wine, oyster sauce, sesame oil, cornflour, spring onions and pepper. Add the chicken and stir. Marinate at least 1 hour. Meanwhile, soak the dried shiitakes in hot water at least 20 minutes. Slice them, discarding the stems.
Drain the rice in a sieve and place in the rice cooker. Add stock and water, then the mushrooms and marinated chicken. Stir.
Turn on the rice cooker and cook according to manufacturer's instructions until the rice is done.