Put pork bones in a large pot and add water until the pot is 2/3 full. Bring to a boil over medium high heat. Turn off heat and discard the liquid. Transfer the pork bones into a colander to cool down. Rinse thoroughly under tap water.

Add pork bones back into the pot and add water again, until 2/3 full. Add ginger and the whole onion. Bring to a boil over medium high heat. Turn to low heat and simmer for 6 hours. Periodically skim the brown foam from the surface of the broth and discard it.

(optional) If there is lean meat attached to the bones, you could choose to leave it to simmer, or take it out and eat it. You can easily separate the meat from the bones with a fork or chopsticks after three hours of boiling. The meat will still be soft and moist. My favorite way is to serve the meat as a snack, with soy sauce and a few slices of ginger for dipping. If you boil the meat for the entire 6 hours, it will be too tough and flavorless to eat.

Turn the heat back to medium high to thicken the broth. The final broth should be about 1/3 the original volume.

Wait until the soup cools off and use an airtight container(*) to store it in the fridge for up to 1 week, or in the freezer for up to 3 months.

The broth can be directly used in a stew or as a soup base. Add water to dilute the broth to desired consistency if using in soup.

(optional) The first batch of broth is ready but the bones can be boiled again to make more broth. You can fill the pot halfway with water and boil another 2 to 3 hours. Store the broth the same way.