1 Halve lemongrass crosswise and flatten with the side of a knife blade.
2 Coarsely chop the lime leaves. Peel the ginger and garlic and cut into fine strips.
3 Peel and thinly slice carrots.
4 Halve leek lengthwise, rinse well and drain. Cut the white and light-green parts into 2 cm (approximately 3/4-inch) pieces.
5 Cut 2 pieces of aluminum foil to 30 x 30 cm (approximately 12 x 12 inches) and spread each with 1 teaspoon oil.
6 Rinse the chicken, pat dry and place on foil pieces, then season with salt and pepper.
7 Scatter the prepared ingredients over the chicken and season lightly with salt and pepper.
8 Fold foil over contents to enclose, leaving a small opening for the liquid.
9 Squeeze juice from lime. Stir 2 teaspoons juice into the coconut water and pour into the foil packet.
10 Seal packet completely, place on a rimmed baking sheet and bake in preheated oven at 200°C (fan oven: 180°C, gas: mark 3)(approximately 350°F) until chicken is cooked through, about 30 minutes. Rinse cilantro, shake dry and pluck leaves. Remove packets from oven, carefully cut open and serve immediately, sprinkled with cilantro.