1 Rinse the fennel and cut into thin strips.
2 Rinse the celery, remove any strings and cut into 5 cm (approximately 2-inch) long pieces and then cut into fine strips.
3 Cook both vegetables in a pot of boiling salted water until crisp-tender, about 2 minutes, then drain and rinse under cold water.
4 Rinse the cherry tomatoes and cut in half.
5 Cut aluminum foil into 2 pieces, each 30 x 30 cm (approximately 12 x 12 inches), and coat 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 lightly season with pepper.
8 Fold foil over contents to enclose, leaving a small opening. Pour half of the white wine into each packet.
9 Completely seal packets, place them on a baking sheet and steam in a preheated oven at 200°C (fan: 180°C, gas mark 3) (approximately 400°F/convection 350°F) until cooked through, about 30 minutes.
10 Meanwhile, rinse the basil, shake dry, pluck leaves and tear into small pieces. Remove packets from the oven and carefully cut open. Serve sprinkled with basil.