Blanch the Bones: In a large pot, add the beef bones and enough water to cover them. Bring to a boil for about 5 minutes, then drain the water and rinse the bones to remove impurities.

Char the Aromatics: On a dry skillet, lightly char the onion and ginger halves until browned and fragrant. This step brings out deeper flavors.

Simmer the Broth: In a clean pot, add the blanched bones, beef brisket, charred onion, and ginger. Add the star anise, cloves, cinnamon stick, and coriander seeds. Pour in 12 cups of water and bring to a gentle boil. Reduce the heat to low and let the broth simmer for at least 3 hours, ideally 4-6 hours for maximum flavor.

Skim the Broth: Occasionally skim off any foam or impurities that rise to the top to keep the broth clear.

Season the Broth: After the simmering period, add fish sauce, sugar, and salt to taste. Remove the beef brisket, set aside (this can be sliced and added to the soup if desired), and strain the broth through a fine-mesh sieve to remove the solids.

Cook the Noodles: Cook the rice noodles according to the package instructions. Drain and set aside.

Slice the Beef Tenderloin: Slice the beef tenderloin paper-thin. If needed, freeze the beef for 15-20 minutes beforehand for easier slicing.

Assemble the Bowls: Divide the cooked noodles among serving bowls. Add a few slices of the raw beef tenderloin on top.

Ladle the Broth: Bring the strained broth back to a boil, then ladle the hot broth over the raw beef in each bowl. The heat from the broth will gently cook the thin beef slices.

Garnish and Serve: Garnish the Pho with green onions, cilantro, Thai basil, mint, bean sprouts, and fresh lime wedges. Add sliced chili peppers, hoisin sauce, and Sriracha for additional flavor, if desired.