Parboil the bones: Place bones and beef shank (if using) in a large pot. Cover with cold water. Bring to a rapid boil for 5–7 minutes. Drain and rinse bones and pot to remove impurities. This keeps the broth clear.

Char aromatics: On a grill, broiler, or dry skillet, char onion halves and ginger until deeply browned and slightly blackened in spots, 5–8 minutes. This adds sweetness and smokiness.

Toast spices: In a dry pan, toast star anise, cinnamon, cloves, coriander seeds, peppercorns, and cardamom until fragrant, 2–3 minutes. Watch closely so they don’t burn.

Simmer the broth: Return cleaned bones to the pot. Add 5–6 quarts of water, charred onion and ginger, and toasted spices (tie spices in a cheesecloth or use a spice ball for easy removal). Bring to a boil, then reduce to a gentle simmer. Skim foam and fat in the first 30 minutes.

Season: After 2 hours, add 3 tablespoons fish sauce, 1 tablespoon sugar, and 1 tablespoon salt. Continue simmering for a total of 3–4 hours (up to 6 for deeper flavor). Taste and adjust seasoning. The broth should be savory, slightly sweet, and aromatic.

Strain and clarify: Remove bones and aromatics. Strain the broth through a fine-mesh strainer. If you like a leaner broth, chill and remove the fat cap before reheating.

Prep noodles: Soak rice noodles in warm water 20–30 minutes until pliable. Cook briefly in boiling water 30–60 seconds until just tender. Rinse with cold water to stop cooking and prevent clumping.

Prepare toppings: Arrange basil, cilantro, mint, bean sprouts, lime wedges, onion slices, and chiles on a platter. This makes the bowl interactive and fresh.

Slice the meat: Freeze sirloin for 15–20 minutes to firm, then slice paper-thin across the grain. For brisket or shank, slice cooked meat thinly. Keep cold until serving.

Assemble bowls: Divide noodles among bowls. Top with raw sirloin slices and/or cooked brisket. Bring broth to a rolling boil and ladle over the meat to cook it just until blush. Finish with scallions and a squeeze of lime. Serve with gluten-free hoisin, sriracha, and tamari on the side.