Simmer the beef brisket for 4–6 hours. Bring water to a boil, add the brisket, and cook. Once boiling, skim off any foam, then lower the heat and simmer for about 2 hours. Turn off the heat, cover, and let cool. Once completely cool, turn the heat back on and simmer for another 2 hours, then turn off the heat, cover, and let cool again. The brisket should be tender.

Once the brisket is tender, add the dry spice bag (star anise, cinnamon, etc.) and 1 onion (halved or whole) to the pot. Simmer for about 30 minutes, then remove the brisket and slice it. This step helps the brisket absorb more aroma. Next, add the beef pho seasoning packet and beef meatballs, and adjust the seasoning to taste.

Chop the scallions, cilantro, sawtooth herb, and onion, then mix them together or keep them separate as you prefer. Thinly slice the rare beef (or buy it pre-sliced).