Heat olive oil over medium heat in a large pot or Dutch oven. Saute onion and celery until onion is soft and translucent.
Add the garlic and ginger; cook 1-2 minutes more.
Add carrots and chicken breast to the pot. Sprinkle chicken with salt and pepper and then pour the chicken broth to cover the chicken. Add lemongrass to the pot if you are using.
Bring soup to a low boil, reduce heat and simmer until chicken breasts are cooked through (~10 minutes for thin-sliced chicken breasts).
When the chicken is cooked through, remove it from the pot and shred with two forks.
Bring the soup up to a boil once again. Return the chicken to the pot, add couscous, turmeric, and lemon juice. Cook 8-10 minutes more, until couscous is cooked through.
Remove pieces of lemongrass.
Serve immediately.
Notes
Storage: Refrigerate for up to 4 days in an airtight container.Notes:This soup is packed with nutrients and healthy ingredients. Garlic, ginger, turmeric, and lemon are all associated with a boost to the immune system. Their inclusion in this soup gives an earthy and ultra-flavorful depth to a fairly traditional chicken noodle soup.The greatest health benefits will come from using fresh ingredients. Ginger can be pretty stringy and difficult to finely mince. I like to just scrape it over a grater. It turns it into almost a paste - you can also purchase ginger paste in the grocery store produce area. Turmeric is softer and easy to grate. Peel both the ginger and turmeric before grating - I use a regular potato peeler, but a paring knife also works.The lemongrass is a lovely addition to the soup. To cook with lemongrass, peel off the hard outer layers. Place the chunks of lemongrass on a cutting board and smash them with the flat of a knife. Add to the soup while it is simmering.