Begin by placing your beef knuckles or leg bones in a large pot and cover with water. Bring to a boil over high heat and boil for 3–5 minutes to remove scum. Drain and rinse the bones, then return to the pot with cold water.

Char the quartered onions and halved ginger under the broiler for 10–15 minutes, turning halfway through until caramelized. This enhances the smoky depth of flavor.

Toast the cinnamon sticks, coriander seeds, fennel seeds, star anise, cloves, and black cardamom in a dry skillet over medium heat for about 5 minutes until fragrant.

With everything prepared, bring the pot of cold water and bones to a boil. Reduce to a gentle simmer and add charred aromatics, spice bag, fine sea salt, fish sauce, and rock sugar. Let simmer uncovered for at least 3 hours.

Carefully remove bones and aromatics using a slotted spoon. Strain the broth through a fine-mesh sieve or cheesecloth to achieve a clear broth.

Soak dried rice noodles in hot water for about 20 minutes until softened, then drain. Bring a pot of water to a boil and briefly boil the soaked noodles for 1–2 minutes.

To serve, place a portion of the cooked rice noodles into each bowl. Top with thinly sliced raw beef, which will cook gently when the hot broth is ladled over it.

Garnish bowls of pho with thinly sliced onions and freshly chopped cilantro. Invite guests to customize with optional toppings. Serve immediately.