Step 1

Prepare the cure the day before by combining the salt, sugar and lemon zest in a small bowl. Remove the skin from the salmon fillets, then run your fingers over the top to check for any small bones and remove.

Step 2

Place the salmon into a shallow bowl and rub both pieces with the cure. Cover with baking parchment or foil, then weigh it down with a couple of cans and chill for at least 6 hours, ideally overnight.

Step 3

Place the garlic in a spice grinder, mini chopper or pestle and mortar. Tear in the coriander and parsley (remove any thick, woody stems) and blend until finely chopped. Remove and discard the seeds from the preserved lemons and add what’s left to the mixture with the cumin, olive oil and chilli flakes. Blitz again until well combined, then tip into a mixing bowl.

Step 4

Finely chop the spinach and add to the herby paste with the mascarpone and lemon juice. Stir well, then set aside. Remove the salmon from the fridge, drain the liquid and rinse well to remove the cure. Pat dry using kitchen paper.

Step 5

Line a baking tray with baking parchment. Lightly flour the work surface and cut ⅔ of the pastry block. Roll it out into a rectangle large enough to fully wrap around the salmon, approx 35x28cm. Place 1 salmon fillet into the centre, then top with the filling. Sandwich the second fillet on top, stacking the thinner end with the thickest part of the bottom layer to create an even-shaped block.

Step 6

Brush the edges of the pastry with beaten egg. Fold the long sides around the pastry, pinching underneath to create a seam, then fold the short ends up to create a parcel. Flip over and place onto the lined tray.

Step 7

Using the remaining pastry, create a lattice (see tip). Brush the top with beaten egg, then stretch the lattice to fully cover the top. Brush again with egg, then chill the en croûte until the pastry is firm. You can make and chill it a couple of hours ahead.

Step 8

When ready to cook, preheat the oven to 200ºC, gas mark 6. Bake for 35-40 minutes, until golden brown all over and cooked through. Allow to rest for 5 minutes, then slice and serve.