Step 1

Soak the pork bones for 1 hour with enough cold water to cover them completely. Rinse 2-3 times until the water runs clear. (If substituting chicken, you can skip this step.)

Step 2

Add the bones to a large, thick-bottomed soup pot, cover with fresh water, cover, and bring to a boil. Once boiling, let it boil for 1 minute, then drain through a colander. Rinse the pork bones clean, drain, and set aside.

Step 3

Wash the pot and dry it thoroughly. Heat it over medium heat, and add the oil, tomato paste (if using), and the tomatoes. Cook for 5 minutes, or until the tomatoes are softened. Add the 9 cups of water, along with the pork bones and corn. Cover, increase the heat to high, and bring the soup to a boil.

Step 4

Once boiling, reduce the heat to medium-low. Cover and simmer for 1 hour (for ribs or chicken) or 90 minutes (for neck bones).

Step 5

Next, add the potato chunks, cover, and bring the soup to a boil once again. Reduce the heat to medium low and simmer for another 30 minutes, until potatoes are tender. Skim off the grease floating on the surface of the soup (optional), and stir in the salt. Serve the soup with salt, so that each person can add more to taste before enjoying. Serve the pork or chicken from the soup with light soy sauce for dipping.