Rinse and drain the rice, and place in a large pot. Stir in the salt and oil, and let stand for 5 minutes.
Add the pork to the rice, and stir in the water. Bring to the boil, then simmer over medium heat for 15 minutes, or until the pork is cooked through. Remove the pork from the pot with a slotted spoon, and set aside. Continue to simmer the rice for 20 minutes. Chop the pork into small cubes, and mix with the salted egg and hundred-year egg.
After the 20 minutes are up, stir the pork and egg mixture back into the congee along with the oyster sauce. Serve in bowls, and garnish with ginger and spring onion. Have soy sauce and pepper on the side for seasoning.
Despite its name, a hundred-year egg has not been around for 100 years! It is an egg, usually from a duck, that has been preserved for 100 days. Look for them in Chinese markets, also known as 'century eggs' or 'thousand-year old eggs'.