How do I cook fish in a paper parcel?

En papillote is steaming with the flavourings trapped in with the fish. It suits exactly the fish that go wrong in a pan — thin, delicate, breakable fillets — because nothing touches them and there is no moment where you have to turn anything over. It is also the only method where you can put the food in the oven and genuinely stop thinking about it.

What you'll need

• Baking parchment or foil
• A baking tray
• A splash of wine, stock, water or lemon juice

Step by step

1. Cut a sheet about twice the size you think you need.Roughly 40cm square for one portion. Too small a sheet is the commonest reason a parcel leaks, because there is nothing spare to fold with.
2. Build a base for the fish to sit on.Thinly sliced fennel, courgette, leek, spring onion or par-cooked potato. It lifts the fillet out of the liquid and it cooks in the same time, so the parcel is a whole dish rather than just fish.
3. Lay the fillet on one half of the sheet, off centre.Skin side down if the skin is on — it will not crisp in a parcel, so consider removing it. Season it now, because you will not get another chance.
4. Add a small amount of liquid, and no more.Two tablespoons of wine, stock, water or lemon juice, plus a knob of butter or a slick of oil. The fish releases its own liquid too. A parcel swimming in liquid boils the fish instead of steaming it.
5. Keep aromatics thin and few.A slice of lemon, a sprig of thyme or dill, a sliced garlic clove, a few capers or olives, a piece of chilli. Anything thick and raw will still be raw when the fish is done.
6. Fold the paper over and seal the edge with small overlapping folds.Bring the free half over the fish. Starting at one corner, make a fold about 2cm deep, then fold again half-overlapping the first, working round the whole open edge like a pasty crimp. Twist the last corner tightly.
7. Leave air inside.Do not press the parcel flat. The trapped air becomes the steam space, and the parcel ballooning in the oven is the visible signal that the seal held.
8. Bake at 200°C for 12 to 15 minutes.A standard fillet of 150 to 180g at that temperature. Thin flat fish takes 8 to 10 minutes; a thick loin 15 to 18. The parcel should be domed and browned in patches.
9. Serve the parcel unopened and let people open it.It keeps everything hot, and the burst of aromatic steam is most of the point. Warn people to open it away from their face — that steam is genuinely hot.

Tips

• Foil works and seals more easily than paper, but do not use foil with a lot of lemon juice, wine or tomato — prolonged contact with acid pits the foil and can taint the dish. Paper for acidic parcels.
• You can assemble parcels several hours ahead and keep them in the fridge, which makes this an unusually good method for cooking fish for guests.
• Prawns, mussels and clams go into a parcel very well and are done at the same time as a fillet.
• If you want any colour on the fish, sear it skin-down for a minute first and build the parcel around it — but accept that the skin will soften again.
• A parcel does not brown the fish at all, so put the flavour in: miso and ginger, harissa and lemon, butter and dill, tomato and olive, coconut and lime.

Common mistakes

• Adding too much liquid — It stops being steaming and becomes poaching in a bag. The fish comes out pale and washed-out, and the sauce is thin and dilute rather than concentrated.
• A loose or single fold — The steam escapes, the parcel never inflates, and the fish half bakes and half dries. The overlapping crimp is what holds the pressure, and one big fold does not.
• Thick raw vegetables in the parcel — Twelve minutes cooks fish, not chunks of carrot or potato. Slice everything thin enough to be done in the same time, or cook it partly first.

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