Begin by charring the quartered onions and halved ginger over an open flame or under a broiler until they're nicely caramelized and fragrant.

In a large pot, combine the beef bones, charred onions, ginger, star anise, cloves, cinnamon sticks, 1 tablespoon of fine sea salt, fish sauce, and yellow rock sugar. Add 6 quarts of cold water and bring to a gentle simmer.

Allow the broth to simmer for 3 hours, skimming off any foam that rises to the surface. This will help create a clear and clean broth.

After simmering, strain the broth through a fine-mesh strainer to remove the solids, and discard the bones and spices.

Refrigerate the strained broth overnight to solidify the fat at the top for easy removal. Once chilled, skim off the fat and reheat the broth before serving.

While the broth is reheating, prepare the pho noodles. Soak dried rice noodles in hot water for 15 to 20 minutes until soft, or rinse fresh noodles with cold water to untangle them.

Cook the noodles according to the package instructions if necessary, and then blanch them briefly in hot water before assembling the bowls.

Thinly slice the raw beef across the grain and set it aside. To serve, place a portion of noodles in each bowl, top with raw beef, and ladle hot broth over the top to cook the meat.

Offer a variety of garnishes, including green onions, fresh herbs, bean sprouts, lime wedges, and chili sauce at the table for everyone to customize their bowls.