Ingredients

Step by step

1. Heat the oven to 200°C, fan 180°C, gas 6. Put the sea salt, egg whites and 2 tablespoons water into a food processor. Using a fine grater, zest the lemon into the bowl of the processor, and add the peppercorns, coriander seeds and fennel seeds. Roughly chop most of the pack of dill and add. Whiz for a few seconds to make a wet, pale green, sandy paste.
2. Pat the salmon fillet dry with kitchen paper, and cut in half to make 2 pieces that will sandwich together. Cut the zested lemon into thin slices. Add the remaining dill sprigs and lemon slices to the flesh of one fillet piece, then sandwich them together with the skin side outside. Tie together using kitchen string if one piece is wider and there’s a lot of exposed salmon flesh.
3. Line a baking tray with foil, put ¼ of the salt mixture into the middle and pat it down flat so it’s a little bigger than the salmon parcel. Place the salmon on top, then press the remaining salt mixture all over and around the salmon to encase it with no gaps.
4. Bake for 40-50 minutes in the middle of the oven – nearer to 40 minutes for a thinner, wider side of salmon, or 50 minutes for a chunkier fillet.
5. Meanwhile, make the sauce. Heat the double cream in a small pan on a very low heat for 15 minutes, whisking every minute or so until reduced by half. Make sure it doesn’t boil. Heat the oil in another small pan. Fry the shallots on low until translucent and tender – about 10 minutes. Add the vinegar and simmer until evaporated, then add the wine and simmer until reduced by half.
6. When the salmon is out of the oven, rest for 10 minutes. A metal skewer inserted into the middle of the parcel should feel hot to the touch.
7. While the salmon is resting, stir the reduced cream into the wine; the mixture will thicken instantly. Keep whisking until you get a smooth sauce. Season with pepper and a small amount of salt. Stir the watercress through the sauce until just wilted, then remove from the heat.
8. Crack open the salt crust with a knife or spoon and discard. Carefully remove the skin and flake the salmon onto plates. Serve with buttered new potatoes and a jug of the creamy watercress sauce.
   Tip

   Salt baking
   A classic chef’s technique. You make an inedible ‘salt dough’ from coarse salt and egg white, and cover food such as meat or fish with it before baking. The method locks in flavour and stops steam escaping, giving a perfect, moist result. The water drawn out of the food helps turn the salt mixture into a hard crust that must be cracked open before serving, and doing this at the table looks really impressive! Salt baking also works well with whole root veg such as celeriac, beetroot and potatoes. Salt can be an irritant, so you might want to wear disposable gloves when applying the dough.