Bring a large stockpot of water to boil on high heat. When water is boiling, place all pork bones into the water. Allow to boil on high heat for 5-8 minutes, or until no more blood/impurities appear in the water.
Discard the water from the bones. Wash the bones of any foam or impurities.
Making the Broth
Place pork bones and 1 gallon water into a large pot. Bring this pot to a boil on high heat, then reduce heat to medium for a simmer. Add in carrots and salt. Allow to simmer on low heat for about 1.5 hours.
Then add Napa cabbage and tomatoes. Simmer another 15 minutes until both are softened.
Add fish sauce. Add additional fish sauce and salt to taste.
Serve hot. The meat from pork bones can also be eaten, usually with a dipping sauce like nuoc mam or soy sauce.
Keyword bone broth, chicken vegetable soup, pork bone soup