In a large pot, bring 1600ml of water to boil. While waiting for the water to boil, rinse the rice and chop the ginger. Also while waiting for the water to boil, prepare the chicken by mixing together thinly sliced chicken with all of the other ingredients (cornstarch, oyster sauce, bullion, and oil) and set aside.
Once the water is boiling, turn the heat down to a low-medium heat, add the rice to the pot, stir and then cover and cook for 25 minutes.
During this wait you can make the marinated mushrooms by heating oil in a small pan. Once it's heated add the mushrooms and move them around for 3-5 minutes until they color lightly then add all of the other ingredients (soy sauce, mirin, sake, oyster sauce, and sugar) and cook for about 7-8 minutes until the sauce thickens and completely coats all of the mushrooms. Set aside.
Uncover the rice and whisk until the grains start to break. If yours do not break after 2 minutes of whisking, simply cook for 5-10 minutes more until they break apart with light agitation (it should start to resemble a thick pudding). You can cook longer or add more water to your liking at this point to adjust texture since it will only cook a few more minutes you want to adjust the thickness now.
Once you're happy with the texture of the congee, add the chicken in batches to the rice. Cook for 1-2 minutes until the pieces of chicken are completely cooked through.
Add the ginger, bullion, and salt to the rice, top with the marinated mushrooms, boiled eggs, and other toppings and serve hot.
4 servings
a bowl