Vietnamese beef noodle soup with ginger

8 whole star anise
1 whole cinnamon stick
6 whole cloves
1 piece (4 inches) peeled fresh ginger
2 medium onions, halved
4 pounds oxtail, rinsed thoroughly
6 scallions, white and pale-green parts only, cut into 2-inch pieces, plus 4 scallions, thinly sliced on the diagonal
1 teaspoon whole black peppercorns
1 teaspoon coarse salt
8 ounces eye of round or sirloin of beef
8 ounces thin rice noodles (rice sticks)
2 shallots, thinly sliced
3/ 4 cup fresh bean sprouts
3/ 4 cup fresh cilantro sprigs
3/ 4 cup fresh basil leaves
1 lime, quartered

Make the stock: Heat the star anise, cinnamon, and cloves in a small, dry skillet over medium-high heat until fragrant, about 2 minutes. Transfer to a 6-quart stockpot.
Preheat the broiler. Broil the ginger and onions, flipping once, until blackened, about 5 minutes per side. Transfer to the pot. Add the oxtail, 2-inch scallion pieces, and peppercorns. Add 5 quarts water; bring to a boil. Skim foam. Add the salt. Reduce heat. Simmer, skimming occasionally, 2 1/ 2 hours.
Pour the stock through a large sieve into a large bowl; discard the solids. Let cool 20 minutes. Pour through a cheesecloth-lined sieve into a large bowl. Refrigerate, covered, 6 hours or overnight.
Make the soup: Chill the beef in the freezer until firm, about 2 hours. Cover the noodles with cold water. Let stand until the noodles are softened, about 30 minutes; drain.
Cut the beef in half. Place each half flat side down, and cut the beef against the grain as thinly as possible. Allow the beef to warm to room temperature.
Skim the fat from the stock; discard. Transfer the stock to a pot; add the shallots, and bring to a boil. Reduce heat, and simmer until the shallots are soft, about 15 minutes.
In a medium pot of boiling water, cook the noodles until just tender, about 10 seconds; drain.
Divide the noodles, beef, and sprouts among 4 bowls. Add the simmering stock (it will cook the beef gently). Top with thinly sliced scallions and herbs; serve each bowl with a lime wedge
SERVES 4