Blanch bones: Place beef bones and chuck/brisket in a large stock pot. Cover with cold water. Bring to a rolling boil over high heat, then boil vigorously for 10-15 minutes, skimming off any impurities that rise to the surface.

Drain and rinse: Drain the bones and beef in a colander. Rinse them thoroughly under cold running water to remove all scum and impurities. Clean the stock pot as well to ensure a clear broth.

Char aromatics: While bones are blanching, place halved onions and ginger on a baking sheet. Broil in the oven or char over an open flame until softened and slightly blackened (about 15-20 minutes in oven, flipping halfway). This step adds a crucial smoky depth and sweetness.

Toast spices: In a dry pan over medium heat, toast star anise, cinnamon stick, cardamom pods, cloves, fennel seeds, and coriander seeds until fragrant, about 2-3 minutes. Place them in a spice bag or cheesecloth sachet to prevent them from floating freely in the broth.

Combine for broth: Return the rinsed bones and blanched beef (chuck/brisket) to the clean stock pot. Add the charred onions and ginger, and the spice sachet.

Add water and simmer: Pour 12-14 cups of fresh cold water into the pot, ensuring everything is submerged. Bring to a gentle boil, then immediately reduce heat to low. Skim any foam that rises to keep the broth clear.

Season the broth: Add rock sugar, fish sauce, and salt. Simmer gently, uncovered, for at least 3-4 hours. The broth should barely bubble; a rolling boil will make it cloudy. Keep skimming occasionally.

Remove beef and continue simmering: After 1.5-2 hours, carefully remove the cooked chuck/brisket (it should be fork-tender). Let it cool, then slice thinly against the grain. Return it to the broth to keep warm or set aside. Continue simmering the bones for the remaining time to extract maximum flavor from them.

Strain the broth: Remove all solids (bones, onions, ginger, spice sachet) from the pot. Strain the broth through a fine-mesh sieve into a clean pot. Skim off excess fat if desired for a lighter broth. Taste and adjust seasoning with more fish sauce or salt if needed. Keep the broth piping hot.

Prepare noodles: If using dried rice noodles, soak in warm water then blanch according to package directions. If using fresh, blanch quickly in boiling water until just tender (usually 15-30 seconds). Drain well and rinse with cold water to prevent sticking.

Arrange garnishes: Arrange the raw thinly sliced beef (sirloin/eye of round), sliced cooked beef (chuck/brisket), bean sprouts, fresh basil, chopped cilantro, sliced green onions, thinly sliced red onion, lime wedges, and sliced chilies on a large platter for communal serving.

Assemble bowls: Divide the hot rice noodles evenly among individual serving bowls.

Add beef: Arrange slices of raw beef (if using) and cooked beef over the noodles. The piping hot broth will cook the raw beef to a perfect medium-rare.

Ladle broth: Carefully ladle the piping hot broth over the noodles and beef, ensuring the raw beef is submerged to cook through slightly.

Garnish: Serve immediately with the platter of fresh herbs, lime, chilies, hoisin sauce, and sriracha on the side, allowing each diner to customize their bowl to their preference.