Step 1Cook the noodles in a large saucepan of boiling water for about 2 minutes. Using tongs, then transfer the noodles to a colander; set aside to drain. Bring the water back to the boil; add chicken. Reduce the heat to low; simmer for 4–5 minutes, or until it is just cooked through. Drain. Transfer the chicken to a plate; then set aside to cool slightly.
Step 2Wipe pan dry. Spray with olive oil; set over medium heat. Add shallots, garlic, ginger and chilli; cook, stirring, for 1 minute. Add stock, 3 cups of water, sesame oil and soy sauce; cover and bring to the boil. Reduce heat to low; simmer, covered, for 5 minutes. Divide noodles among 4 deep serving bowls. Shred chicken.
Step 3Increase heat to medium-high; bring broth to the boil. Then add choy sum and bok choy; cover and cook until wilted. Swirl the soup mixture continuously with a wooden spoon; gradually pour in eggs. Add mushrooms.
Step 4Using tongs, arrange greens and mushrooms over noodles; top with chicken. Then ladle over the hot soup; top with the bean sprouts. Sprinkle with shallots and sesame seeds to serve.