1. Purée the tomatoes, onion, chiles, and garlic in a blender.

2. Heat 2 tbsp of the oil in a large saucepan over medium-high heat. Add the chicken and stir-fry for 2–3 minutes, or until just cooked. Using a slotted spoon, transfer to a plate.

3. Add the remaining 1 tbsp oil to the pan and heat. Reduce the heat to medium-low. Add the noodles and cook, turning once, about 2 minutes, until golden.

4. Add the tomato purèe and stir until the noodles are coated. Stir in the stock and return the chicken to the saucepan. Return the heat to high and cook until the noodles are tender.

5. Ladle the soup into bowls and top each serving with a dollop of sour cream and some avocado cubes. Serve hot.

Variation:

Chinese Chicken Noodle Soup: Soak 6 dried Chinese mushrooms in 1¼ cup boiling water for 30 minutes. Strain the soaking water into a large saucepan and add 2½ cups chicken stock. Slice the mushrooms and cut 2 boneless, skinless chicken breasts into thin strips. Break up 6oz (175g) rice vermicelli into short lengths, stir into the stock, and bring to a simmer. Cook for 2 minutes, then add the mushrooms, chicken, and ¾ cup fresh or thawed frozen corn. Simmer until the noodles are tender, about 2 minutes more. Spoon into bowls and serve at once.