Roasted salmon with lemon beurre blanc

Wash and finely slice the leeks, then cook them gently with a knob of butter and a pinch of salt.

• Cover for 8 minutes, then uncover to evaporate the water.
• Do not let them brown.

Look for this: They are very tender but still pale green.

Pat the fillets dry, remove any pin bones and season on every side.

• Place skin-side down in a lightly oiled dish.
• Add zest now, but not the juice.

Look for this: The surface of the fish is dry and satin-like.

Roast according to thickness and remove the salmon before the centre turns completely opaque.

• Allow about 12 minutes for a 3 cm fillet.
• Rest for 2 minutes.

Look for this: The flakes separate under light pressure while the centre stays pearly.

Reduce the lemon juice to one spoonful, lower the heat and whisk in cold butter one cube at a time.

• Never let the sauce boil.
• Serve immediately with the leeks and salmon.

Look for this: The sauce is glossy, supple and coats the back of a spoon.