Cut 4 pieces of nonstick baking paper, each 30 cm (12 inches) square. Put a haddock fillet in the centre of each piece and arrange some of the coriander, chilli, shallot, lime and chopped lemon grass stalk evenly over each. Wrap them up into neat parcels.
Transfer the parcels to a baking sheet and cook in a preheated oven, 180°C (350°F), Gas Mark 4, for 20 minutes.
Meanwhile, put the rice in a pan with 400 ml (14 fl oz) water, the bashed lemon grass stalk and the lime leaves. Cover and simmer for 12 minutes. When the rice is cooked and the water absorbed, stir in the coconut milk. Serve with the haddock parcels, with some extra lime halves.