Heat a cast-iron skillet over high heat. Place the onion and ginger cut-side down, and char deeply, about eight to ten minutes.
1 large onion, 4-inch piece ginger
Place the beef bones and brisket in a large pot, cover with cold water, and bring the liquid to a boil. Boil for ten minutes, then drain, and rinse the bones and pot thoroughly.
2 pound beef bone, 1½ pound beef brisket or oxtail, cold water
Toast the spices in a dry skillet over medium-low heat until fragrant, about five minutes. Remove the skillet from the heat.
6 whole star anise, 3 cinnamon stick, 2 green cardamom pod, 1 teaspoon coriander seed, 1 teaspoon fennel seed
In a clean stockpot, combine the bones, brisket, charred onion, charred ginger, garlic, and daikon. Wrap the toasted spices in cheesecloth, and tie it with twine to make a sachet. Add the sachet to the pot.
½ daikon radish, 6 garlic clove
In the same stockpot, add MSG, salt, fish sauce, and enough cold water to fully cover the contents. Bring the liquid to a boil, then reduce the heat to a very gentle simmer. Skim foam as needed.
1 teaspoon MSG, 1 tablespoon kosher salt, 2 tablespoon fish sauce
Simmer uncovered for six hours, maintaining a low simmer and topping off with water as needed.
Remove the bones and solids. Reserve any tender meat. Strain the broth through a fine-mesh sieve. Taste and adjust the seasoning with salt, fish sauce, or rock sugar.
2 teaspoon rock sugar
Chill the broth overnight. Remove and discard the solidified fat from the surface before reheating.