Gather all your ingredients: shredded cooked chicken, lemongrass, ginger, carrots, celery, and aromatics.
Slice the lemongrass stalks into thin rounds and bruise them gently with the side of your knife to release more flavor.
Heat a large heavy-bottomed pot over medium heat and add the oil. Once shimmering, sauté diced onion until translucent and fragrant, about 5 minutes.
Add minced garlic, sliced ginger, and bruised lemongrass to the pot. Cook for about 2 minutes until fragrant, listening for a gentle sizzling and smelling the zesty aroma.
Toss in the chopped carrots and celery. Stir well and cook for another 5-7 minutes until they start to soften and release their sweet aroma.
Pour in the chicken broth, increase the heat to bring it to a gentle boil, then reduce to a simmer. Add the shredded chicken and season with salt and pepper.
Let the soup simmer uncovered for 20-25 minutes, allowing the flavors to meld and the vegetables to become tender.
Taste the broth and adjust seasoning if needed. Squeeze in a bit of lime to brighten the flavors just before serving.
Remove the lemongrass stalks from the pot before serving. Ladle the hot soup into bowls and garnish generously with chopped cilantro or Thai basil.
Serve the soup hot, with an extra squeeze of lime or a sprinkle of herbs if desired. Enjoy the bright, comforting flavors that remind you of Southeast Asian markets!