Gather all your ingredients, including bruised lemongrass and sliced galangal, ready for quick layering of flavors.
In a large heavy-bottomed pot, sauté sliced shallots and minced garlic over medium heat until fragrant and slightly translucent, about 3 minutes, filling the kitchen with a sweet and savory aroma.
Add the chicken breast, cooking until it turns opaque and is just cooked through, approximately 4-5 minutes. Use a wooden spoon to break up the chicken slightly as it cooks.
Pour in the chicken broth, then add the bruised lemongrass stalks, sliced galangal, and a pinch of chili flakes. Bring the mixture to a gentle simmer and let it bubble softly for 15 minutes to develop a rich, fragrant broth.
Remove the lemongrass and galangal slices from the broth, discarding or setting aside the herbs for another use.
Stir in freshly squeezed lime juice and fish sauce, tasting the broth and adjusting seasoning as needed for balance and brightness.
Add chopped cilantro, Thai basil, and mint leaves just before serving. Allow the herbs to wilt slightly in the hot broth, releasing their vibrant aromas.
Give the soup a final stir, then ladle it into bowls, making sure each serving has plenty of herbs, tender chicken, and a fragrant, tangy broth.
