To begin, preheat your oven to 220°C (430°F). Arrange the beef bones, onion, and ginger on a baking sheet. Roast for 15-20 minutes, turning once, until the bones are browned, and the onion and ginger are slightly charred. This step deepens the flavour of the broth.

Transfer the roasted bones, onion, and ginger to a large stockpot. Fill the pot with 4 litres of water and bring to a boil. Reduce the heat to a gentle simmer and skim off any foam or impurities that rise to the surface. Simmer for 3 hours to extract maximum flavour.

While the broth simmers, toast the star anise, cinnamon sticks, cardamom pods, cloves, and coriander seeds in a dry skillet over medium heat until fragrant. Add these spices to the broth for an aromatic base. Continue simmering for an additional hour.

Add the beef brisket to the simmering broth during the last 60 minutes of cooking. This will cook the brisket while infusing the broth with its richness. Remove the brisket and set it aside to cool before slicing thinly.

After 4 hours of simmering, strain the broth through a fine mesh sieve into a clean pot to remove solids. Add fish sauce, sugar, and salt to season the broth. Taste and adjust the seasoning, balancing the savoury, sweet, and salty flavours characteristic of Phở.

Cook the rice noodles according to the package instructions. Drain and rinse under cold water to stop cooking. Divide the noodles among four serving bowls.

Arrange the sliced beef sirloin, brisket, and desired toppings (bean sprouts, fresh herbs, spring onions, and chili) over the noodles. Pour the hot broth over the ingredients in each bowl, ensuring the beef is slightly cooked by the heat of the broth.

Serve the Phở immediately, accompanied by lime wedges, Hoisin sauce, and Sriracha for individual customization. Encourage diners to add fresh herbs and a squeeze of lime for a burst of freshness. For an authentic touch, pair the soup with a traditional Vietnamese iced coffee or jasmine tea.