In a bowl, soak the brisket in water to draw out blood. Refrigerate until ready to use.
1 pound beef brisket or shank
Rinse the beef bone marrow and then place in a pot and fill with enough water to cover. Bring to a boil over high heat then lower the heat to let it simmer for 5 minutes to let the scums out.
2 pounds meaty beef bone marrow
Drain and discard the water and clean the pot. Rinse the bones again to make sure no scum is left.
Return the beef marrow to the clean pot and fill with 8-10 cups of water to cover. Bring to a boil over high heat. Once it boils cover the pot and reduce heat to achieve a medium boil. Let it boil for an hour or 30 minutes if using pressure cooker.
8-10 cups water
Add the soaked brisket (water drained), fish sauce, onion, the white part of onion leek, and peppercorns. Boil until meat is fork-tender, about 1.5 to 2 hours more or 30 minutes if using a pressure cooker. Add more water if needed to cover the meat.
1 tablespoon peppercorns, ¼ cup fish sauce, 1 medium onion, 2 stalks onion leeks
Turn the heat off to let the fat settle on the surface. Skim off most of the fats then turn the heat back on and bring to a gentle boil.
Add the potatoes and cook for 10 minutes or until tender. Then add the corn and cabbage and cook for 3-5 minutes. Lastly, add the green part of the onion leeks and salt if still needed then turn off the heat.
3 medium potatoes, 2 ears sweet corn, 1 small cabbage, Salt as needed
Transfer to serving bowls.