Step 1Peel then slice the ginger into 4 or 5 coins. Smack with the flat side of a knife or meat mallet and set aside. Thinly slice the green parts of the green onion to yield 2 to 3 tablespoons, and set aside to use as a garnish. Cut the leftover sections into 2- to 3-inch lengths, bruise, then add to the ginger.
Step 2Coarsely chop the leafy tops of the cilantro to yield 2 tablespoons; set aside to use as a garnish. Set the remaining cilantro sprigs aside.
Step 3In a 3- to 4-quart pot, toast the coriander seeds and clove over medium heat until fragrant, 1 to 2 minutes. Add the ginger and bruised green onion sections. Stir until aromatic, about 30 seconds.
Step 4Remove the pot from heat for about 15 seconds to briefly cool, then pour in the broth. Add the water, cilantro sprigs, chicken, and salt. Bring to a boil over high heat, then lower the heat to gently simmer for 30 minutes.
Step 5While the broth simmers, soak the rice noodles in hot water until pliable and opaque. Drain, rinse, and set aside.
Step 6After 5 to 10 minutes of simmering, the chicken should be firm and cooked through (press on it and it should slightly yield). Transfer the chicken to a bowl, flush with cold water to stop the cooking, then drain. Set the chicken aside until cool enough to handle, then cut or shred into bite-size pieces. Cover loosely so the chicken does not dry out.
Step 7When the broth is done simmering, strain it through a fine-mesh strainer into a 2-quart (2-literl) pot; line the strainer with muslin or cheesecloth for super clear broth. Discard the solids. You should have about 4 cups broth. Season with fish sauce and sugar, if needed, to create a strong savory-sweet note.
Step 8Bring the strained broth to a boil over high heat. Put the noodles in a noodle strainer or mesh sieve and dunk in the hot broth to heat and soften, 5 to 60 seconds. Lift the noodles from the pot and divide between the 2 bowls.
Step 9Reduce the heat to keep the broth hot while you arrange the chicken on top of the noodles and garnish with the chopped green onion, cilantro, and a sprinkling of pepper. Taste and adjust the broth’s saltiness one last time. Return the broth to a boil and ladle into the bowls.