Oyster Sauce Chicken and Potatoes Stew | 蚝油土豆焖鸡

Ingredients: 1 whole chicken (or 4 whole chicken legs) 3 potatoes 1 onion 1 green onion 1 cup leek 1 cup shiitake mushroom (optional) 2 cloves garlic 4 slices ginger 1 tbs oil 1 tbs oyster sauce 1/2 tsp salt 1/2 tsp chicken powder 1/2 tsp black pepper 1 tsp dark soy sauce 1 tsp shaohsing cooking wine