Place a large dutch oven or pot over medium heat and add oil. Add the onion, carrot, celery and garlic and slowly saute, adjusting heat to keep them from browning, until soft and translucent, about 10 minutes.
Add the ground turmeric and minced ginger, saute for around 30 seconds to let the spices cook.
Add the chicken stock, chicken breast, rosemary and thyme. Wait, without increasing the heat, until the stock comes to a low simmer. Don't be tempted to increase the heat at this point, to speed up the simmer as doing this can make the chicken tough.
When the soup reaches a simmer, add the couscous. Cook for 20 mins, or until the chicken is cooked through.
Once the chicken is cooked, remove with a slotted spoon and transfer to a cutting board to shred with two forks
Add chicken back to the pot then stir in the peas. If you find that you don’t have enough broth you can add in another cup.