1 Clean the mushrooms and cut into slices.
2 Peel the carrots. Cut lengthwise into thin slices and then into thin strips.
3 Combine the carrot strips with 5 tablespoons of broth in a pot. Add sliced mushrooms and bring to a boil. Cover and cook over medium heat for about 5 minutes. Season with salt and pepper.
4 Cut out 4 large pieces of foil (about 30 x 30 cm) (approximately 12 x 12 inches) and place on a work surface. Fold up the edges a bit to keep juices from escaping.
5 Divide vegetables among the foil packets. Rinse the fish fillets, pat dry and place on the vegetables. Season with salt and pepper.
6 Rinse the lemongrass and peel off the tough outer layer. Trim tough root end. Chop the soft interior finely and sprinkle over the fish fillets.
7 Drizzle 2 tablespoons vegetable broth over each packet. Fold the foil tightly to enclose the contents and cook on hot grill until fish is opaque throughout, 12-15 minutes. Carefully open to serve.