Thai noodle broth
Cook the egg or rice noodles, whichever you're using, if you're using them, following the instructions on the packet, then drain them and rinse through with cold water. Drain again.
To make the paste, whizz the bunch of coriander, the chopped lemongrass stalk, the peeled garlic, the light soy sauce, the fish sauce, the caster sugar and the de-seeded chilli together with the 2 tablespoons of water in a food processor. Whizz for 1-2 minutes, or until a smooth paste has formed.
Put a large saucepan on a medium heat and add the sunflower oil. When it is hot, add the paste and cook for 1 minute, then add the coconut milk and the chicken stock and gently warm through for 5 minutes. Add the peeled, raw tiger prawns and the cooked noodles, if you're using them, and cook for a further 2 minutes until the prawns are opaque and firm.
To serve, stir in the sliced chilli, the basil leaves, the lime juice and the fish sauce, and pour into warmed bowls.