To PrepBreak up the egg in a measuring cup. Then crack the salted egg yolk, carefully pour the yolk into the other half of the shell, letting the white drip into the measuring cup. Repeat this step, shifting the yolk from one shell to the other, until all of the white is sitting in the measuring cup. The cracked egg and salted egg white will be measuring at about 100ml. If so then add 150ml water into the egg mixture, gently stir well and set aside. Ratio of the eggs and water should be 1:1.5In a separate bowl, break up the raw salted egg yolk using a fork. Then peel and cut up the century egg. Place both the salted egg yolk and the century egg in a shallow plate. Set aside.Heat up the steamer or wok with boiling water.While waiting for water to boil, gently stir the egg mixture in the measuring cup again and pass through a sieve into the shallow plate. Place a piece of aluminium foil on top of the shallow plate to prevent the water drips from the lid onto the egg mixture. To CookPut the dish into the steamer or wok. Lower the heat to medium and steam for 5 minutes and then another 3 minutes at low heat to just set. Occasionally lift up the lid to let the steam to escape.Garnish with chopped spring onions, a dash of pepper and drizzle with some sesame oil. Serve immediately.