small bunch of coriander or Thai basil leaves, roughly chopped
Lightly smash the lemon grass with a rolling pin so it is broken but still whole.
In a pan heat, lemongrass, stock, lime leaves, chilli and ginger, bring to the boil, turn down the heat and simmer for 5 minutes.
Remove the lime leaves, ginger and lemon grass and add the fish sauce, carrot and pepper, simmer for 5 minutes then add the chicken, bok-choy and spring onions, simmer for 3 minutes. Check for flavour balance as you may need to add a little more fish sauce or lime.
Serve with a generous topping of fresh herbs. If you like your Thai food spicy, serve with extra chopped chilli.