Step 1Lightly spray a large saucepan with olive oil and place it over medium-high heat. Sauté onion for 5 minutes, or until softened. Add paste and cook, stirring, for 2 minutes, or until fragrant.
Step 2Add mushrooms and cook, stirring, for 1 minute. Add chicken breasts, chicken stock and 3 cups of water, and bring to the boil. Reduce heat to low and simmer, partially covered, for 10 minutes, or until the chicken is cooked through. Transfer chicken to a clean board and set aside to cool slightly. Shred the chicken.
Step 3Meanwhile, cook the noodles in a saucepan of boiling water according to packet instructions, or until al dente. Drain well.
Step 4Add shredded chicken, snow peas and pak choy to the soup, and simmer for 1–2 minutes, or until greens are just tender. Stir through lime juice to taste.
Step 5Divide noodles and soup between 4 bowls. Garnish with coriander leaves, if using.