Place the chicken pieces, sliced onion, and crushed garlic into a large heavy-bottomed pot. Pour in water and bring to a gentle simmer over medium heat, skimming off foam as it rises.
Simmer for about 45 minutes until the chicken is cooked through and tender, filling your kitchen with a warm, savory aroma.
Remove the chicken pieces from the pot and set aside to cool slightly. Strain the broth through a fine mesh strainer into a clean pot, discarding solids.
Add the sliced ginger, bruised lemongrass stalks, and fish sauce into the strained broth. Bring to a gentle simmer and cook for about 10 minutes, letting the flavors meld.
While the broth simmers, shred the cooled chicken into bite-sized pieces, removing bones if using bone-in pieces.
Return the shredded chicken to the broth, stirring gently. If using noodles or rice, add the cooked grains now, allowing them to heat through.
Just before serving, add fresh greens to the hot broth and let them wilt for about 1-2 minutes, creating a vibrant contrast in color and texture.
Taste the broth and adjust with additional fish sauce if needed. Ladle the hot soup into bowls, ensuring each has a good mix of chicken, greens, and broth.
Enjoy this fragrant, bright chicken soup as a nourishing meal that warms both body and soul.
