Heat the oil in a 3-quart soup pot over medium heat. When the oil is hot, add the onion and cook until tender and fragrant, about 2 minutes.
Trim 1 inch away from the white end of the lemongrass, then cut off the green tops of the stalk and discard. Bash the lemongrass with the flat end of a meat mallet until the stalk is flattened. Cut the stalk in half, then slice one half lengthwise into strips, and finely mince the other half.
Add the garlic and minced lemongrass to the pot, give a good stir and cook for another 2 minutes. Stir in the white beans, artichokes and soy sauce. Season with 1/2 teaspoon salt and pinch of pepper and give another good stir. Add the Basic Chicken Stock and shredded chicken, drop the remaining lemongrass strips into the soup and allow to simmer for 30 minutes.
Remove any large lemongrass strips before serving. Garnish with freshly torn parsley or cilantro as desired.
Basic Chicken Stock:
Yield:4 to 6 cups
Cut the chicken carcass bones in half, through the backbone. Place all of the chicken bones into a soup pot along with the carrot, celery, onion and parsley stems. Pour water into the pot until all of the ingredients are covered. Bring the pot to a boil over medium-high heat. When the water reaches a boil, reduce the heat to low. Allow the stock to simmer over low heat, uncovered, occasionally skimming off any foam that forms on the top, for 2 hours.
Strain the stock through a fine-mesh strainer. Discard the bones and vegetables. Use the stock immediately, or chill the stock overnight in the refrigerator. The next day, remove any fat and solids that have gathered on the surface. The stock will keep in the refrigerator for up to 5 days, or can be frozen for future use.