Preheat the oven to 200C/Gas 6. Take 4 large pieces of greaseproof paper, each 4 times larger than each piece of fish, and fold each in half.
Layer the potato slices
on one half of the paper.
In a bowl, toss the tomatoes, olives, lemon juice, chilli, olive oil, salt and pepper. Pat the fish fillets dry and season both sides with salt and pepper.
Place a piece of fish on top of the sliced potatoes in each packet, gently add the tomato-olive mix on top and then a sprig of thyme. Add a splash of white wine to each. To seal, fold the other half of the parchment over the fish, crimping to seal like a Cornish pasty (ensure it is tightly sealed so no steam escapes during cooking).
Place the parchment packets on a baking sheet and bake for 20-25 mins, when the fish should flake easily with a fork. Serve with green veg and grains.
Recipe by appetite magazine at https://www.appetitemag.co.uk/cabillaud-en-papillote/