Preheat the oven to 200c. 

Peel and finely chop 2 large shallots. Roughly chop 100g baby spinach, a  bunch of flat-leaf parsley (stems removed), and 100g baby leaf watercress. 

Fry the shallot in a little olive oil, on a medium-low heat, till translucent; around 8 minutes. 

Add the chopped vegetables, along with the zest and juice of 1 lemon, and a good grating of nutmeg. Cook down for 3-5 minutes, then add 1 tbsp crème fraiche (or for a dairy-free version, substitute with soy yoghurt or the M & S coconut pot. 

Tip into a sieve over a bowl (to capture the juices), and press to squeeze out more of the juices. Let cool.

Meanwhile, blitz 100g baby watercress with 200g crème fraiche (or non-dairy substitute as above) in a food processor, adding most of the juices from the bowl. Season with sea salt and pepper and more lemon juice (to taste).

Take a 500g piece of salmon fillet (skin removed) and slice in half sideways so you can open it up like a book. Spoon the cooled filling into the fillet and fold back over to close. Set aside.

On a baking tray lined with greaseproof paper, place a pre-rolled puff pastry – gluten-free works fine too (320g), width-wise, with half the pastry off the sheet. Place the salmon in the centre of the pastry. 

Dab water around the edge of the pastry, using your finger and then carefully fold over the other half of the pastry. Press the edges with a fork to seal. Score the top with a knife, then beat and brush over an egg.

Bake the salmon in the oven for 20 to 25 minutes, or until the pastry is crisp and golden.

Serves 4.

Serve with the watercress sauce and Romanesco broccoli and new potatoes.

To serve 6: increase the salmon portion to 800g and use two 250g sheets of puff pastry, one on the bottom and one to cover.