Prepare the ingredients: cut the Chicken into serving-sized pieces and rinse, then pat dry; wash and roughly chop the Lá Giang Leaves and set aside.
Peel and thinly slice the Shallots and mince the Garlic; bruise and thinly smash the Lemongrass stalks to release aroma.
Heat a tablespoon of Cooking Oil in a large pot over medium heat, then sauté the shallots and garlic until fragrant and lightly golden.
Add the chicken pieces to the pot and sear briefly on all sides to color the skin and develop flavor.
Pour in enough Water to cover the chicken by about an inch, add the bruised lemongrass, and bring to a gentle boil; reduce heat to a simmer and skim any foam from the surface for a clear broth.
Season the simmering broth with Fish Sauce, a pinch of Salt, and a small amount of Sugar to brighten the flavors; adjust to taste as it cooks.
Simmer the chicken for 20–30 minutes, or until tender and cooked through, then add the chopped Lá Giang Leaves and continue cooking just 3–5 minutes until the leaves are wilted and the soup is pleasantly sour.
Taste and adjust seasoning with more fish sauce, salt, or sugar if needed; if you like heat, add sliced Bird's Eye Chilies to the pot or serve on the side.
Finish the soup by stirring in chopped Scallions and torn Rice Paddy Herb right before serving to preserve their fresh aroma.
Ladle the canh gà into bowls and serve hot with steamed rice or as part of a family-style Vietnamese meal.
