Vietnamese Beef Pho

For 4 servings, prepare 1500 g beef bones, 400 g rice noodles, 300 g thinly sliced beef, 4 star anise, 2 cinnamon sticks, 50 g ginger, 1 onion, 3 tablespoons fish sauce, 100 g bean sprouts, 2 limes, and 20 g basil. Soak the bones in cold water for 1 hour to draw out blood. Blanch them in boiling water, then scrub the surfaces under cold water to remove the residue that would cloud the broth. Toast the star anise and cinnamon in a dry pan for 1 to 2 minutes, stopping when their aroma becomes pronounced. Char the ginger and onion directly over a flame until the outsides darken, then brush away only the loose burnt flakes. Place the cleaned bones, charred aromatics, and toasted spices in a large pot with 3 L water. Keep the pot at a low simmer for 6 to 8 hours and skim foam from the surface as it rises. Strain out the bones and aromatics when the broth is clear and golden. Add the 3 tablespoons fish sauce in portions, tasting between additions so the seasoning does not overwhelm the long-cooked broth. Soak and cook the rice noodles, then divide them among four bowls. Lay the thin beef slices over the noodles and pour the boiling broth directly on top. The heat of the broth cooks the thin meat in the bowl. Serve with the bean sprouts, lime, and basil so each bowl can be adjusted with fresh crunch, acidity, and herbs at the table.