Heat the oil over high heat and toss in the chicken pieces when the pot is hot. Stir the chicken after 1-2 minutes (some pieces should have a bit of browning). Leave it cooking for another minute.
The chicken should be partially cooked at this point. Add in the rice and water and stir. Then add in sliced ginger and garlic.
Cover the pot and let boil. Then turn the heat to low and simmer for 1-2 hours, until the congee is thick and glossy. Mix every 20 minutes or so.
Once the congee is cooked, scoop the miso paste into a separate small bowl. Add in some of the hot congee to the same bowl and mix to dissolve the miso. Once the mixture is well combined, scoop it back into the pot.
Add in the chopped green onions and salt to taste, and mix well one last time. Enjoy!