1 large onion, halved and sliced
1 head garlic, cloves separated but unpeeled
1 2-inch piece fresh ginger, cut into coins
3 or 4 star anise pods
1 cinnamon stick
2 bay leaves
2 tablespoons black peppercorns
6 cups vegetable stock
1/4 cup soy sauce, plus more to taste
1 tablespoon cider vinegar
1 bunch fresh cilantro
1/2 pound mushrooms (any kind), trimmed
8 ounces thin rice vermicelli
6 cups boiling water
4 scallions, sliced, for garnish
2 or 3 limes, cut into wedges, for garnish
Additional toppings (optional; i.e. grated carrots, sliced steamed bok choy, bean sprouts, shelled edamame, pickled ginger, or whatever else you’d like)
1. Put the oil in a large pot over medium heat. When it’s hot, add the onion, garlic, and ginger. Sprinkle with some salt and the sugar and cook, stirring occasionally, until the vegetables soften, 3 to 5 minutes. Add the star anise, cinnamon, bay leaves, and peppercorns and stir until warm and fragrant, no more than a minute. Add the stock, soy sauce, vinegar, half the cilantro (save the rest for garnish), mushrooms, and 1 cup water. Bring to a boil, then lower the heat so the stock bubbles gently. Cook, partially covered, until you are happy with the concentration of flavor, 30 to 60 minutes.
2. Put the rice vermicelli in a large bowl, sprinkle with salt, and cover with the boiling water. Soak until the noodles are barely tender; start checking after 3 minutes. Drain the noodles, then rinse them and the bowl with cold water to cool down. Return the noodles to the bowl, add enough cold water to cover, and let sit until you’re ready to serve.
3. Strain the broth through a fine-meshed strainer, return it to the pot, and keep at a gentle bubble. Taste and adjust the seasoning, adding more soy sauce if you’d like. (You can make the broth to this point, cool, and store it in the refrigerator for several days or the freezer for a few months. Return it to a boil and keep hot until time to serve.)
4. Prepare any additional toppings and put them in bowls or platters. Drain the noodles and divide them among big bowls; ladle some broth over the noodles. Garnish with the scallions, limes, and sprigs of the reserved cilantro. Top the soup with other additions as you like.