Combine rice, ginger, ham bone, and 12 cups (2.8 liters) water in a large pot. Place on stove, cover, and bring it to a boil. When water comes to boil, remove the lid. Reduce heat and allow it to simmer for about an hour.
Add ham, salt, and pepper. Continue to cook for another 30 minutes or until porridge (congee) is thick and ceamy. If porridge gets too thick at any point, stir in ½ cup (120ml) or more water to dilute to preferred consistency.
Serve porridge (congee) warm in individual bowls. Sprinkle with green onions, ginger, and fried shallots. Drizzle with sesame oil and season with pepper and soy sauce. Add yew char koay, if desired.