Preheat the oven to 220°C (430°F). Arrange the Beef marrow bones on a roasting tray and roast for 25–35 minutes until the marrow is browned and fragrant; this step deepens the flavor of the soup.
Meanwhile, prep the aromatics and vegetables: roughly chop the Onion, crush the Garlic, slice the Ginger, bruise the Lemongrass stalks, and cut the Carrot, Potato, Celery and Tomato into bite-sized pieces.
In a dry pan over medium heat, toast the whole spices — the Cinnamon stick, Star anise, Cloves, Green cardamom pods, Black peppercorns, Coriander seeds and Fennel seeds — until aromatic, about 1–2 minutes. Transfer them to a spice sachet or tie them in cheesecloth if you prefer easy removal later.
Heat a splash of Neutral cooking oil in a large soup pot over medium heat. Add the chopped Onion and cook until translucent, then add the Garlic and Ginger and cook another minute until fragrant. Add the bruised Lemongrass and the toasted spice sachet and stir to combine.
Add the roasted Beef marrow bones to the pot and pour in enough Water to cover the bones by a couple of inches. Bring to a gentle boil, then reduce to a low simmer. Skim any foam or impurities from the surface during the first 15–20 minutes.
Simmer the broth gently, partially covered, for 2–3 hours so the marrow and bones release their rich flavor. Break the bones occasionally with tongs or a spoon to expose the marrow and encourage flavor transfer; remove the spice sachet if used.
Add the prepared Carrot, Potato, Celery and Tomato to the pot and continue simmering another 15–25 minutes, until the vegetables are tender and the soup is well flavored.
Season the soup with Salt and a little Sugar to balance the flavors; taste and adjust seasoning as needed.
Ladle the hot Sup Tulang into bowls and garnish with sliced Spring onion, chopped Fresh coriander (cilantro) and a sprinkle of Fried shallots. Serve with wedges of Lime for squeezing over each bowl just before eating.
