Asian chicken noodle soup

Name: Asian chicken noodle soup
Prep time: 20 min
Cook time: 15 min
Total time: 35 min
Cuisine: Asian
Ingredients: 4 boneless skinless chicken breasts; 60ml sake (if you don't have sake, use vodka); thumb-sized piece ginger , peeled and sliced into matchsticks; 3 spring onions , finely sliced on the diagonal, and white and green parts separated; 150ml soy sauce; 4 tsp sesame oil; 2 garlic cloves , grated; 600g thick white noodles (such as udon); 2 large long red Serrano chillies , seeds left in and sliced on the diagonal; 1 large egg , beaten; small pack coriander; 2 tbsp toasted sesame seeds; seaweed flakes, to serve (optional)