Prepare the salmon filling

• Blanch the spinach, squeeze out all the water and chop it.
• Mix the spinach with the crème fraîche, Dijon mustard and chopped dill, then season.
• Season the salmon fillet with salt and pepper and sear it briefly in olive oil on both sides, then chill.

Wrap the Wellington

• Lay the puff pastry out and spread the spinach mixture over the centre.
• Place the salmon on top and fold the pastry around it, sealing the edges well.
• Brush the pastry with beaten egg and chill.

Bake the Wellington

• Heat the oven to 200 °C.
• Bake the Wellington on a baking tray until the pastry is golden and crisp.

Make the potato purée

• Boil the potatoes in salted water until tender, then drain.
• Mash or press the potatoes through a sieve.
• Beat in the warm milk and part of the butter until smooth and creamy, then season.

Cook the asparagus

• Blanch the asparagus in salted boiling water until just tender.
• Drain and toss with a little butter, salt and pepper.

Make the burnt butter

• Melt butter in a pan and cook until the milk solids turn golden brown and nutty.
• Keep warm.

Make the beurre blanc

• Simmer the shallots with the white wine and white wine vinegar until reduced by half.
• Add the cream and reduce slightly.
• Off the heat, whisk in the cold butter piece by piece until the sauce is glossy, then season.

Plate and serve

• Slice the Wellington and serve with the potato purée, asparagus, burnt butter and beurre blanc.