Heat the vegetable oil in a large saucepan over a moderate heat. Quickly brown the chicken breasts all over then remove and set aside.
Add the chilli, onion and garlic to the pan and brown. Stir in the peanut butter and soy sauce, then gradually add the stock.
Bring to a gentle simmer, add the chicken, then keep at a very low simmer for 30 minutes.
Using two forks, shred the chicken while in the soup. Add the coconut milk and salt, adjusting the season as necessary. Continue to simmer on the low heat.
Meanwhile bring a large pan of salted water to the boil, add the rice noodles and cook until al dente. Drain, then add the noodles to the soup.
Serve hot, garnished with the peanuts and coriander.