Heat the butter and olive oil in a large frying pan and add the halibut cheeks or fillets. Cook over a medium-low heat for about 8 minutes, turning once.
Meanwhile, start to make the sauce. Put the shallots or onion into a small saucepan with the wine vinegar, white wine and 6 tbsp cold water. Bring to the boil, then simmer until almost all of the liquid has evaporated.
While the liquid is reducing, put the samphire or asparagus on to cook in simmering water – only add a pinch of salt to the asparagus, as the samphire is salty enough. It will take 3 or 4 minutes to cook.
Stir the cream into the shallot or onion mixture and cook gently for a few moments, then remove from the heat and whisk in the butter, a little at a time, to give a smooth sauce. Add the chopped tarragon and season with a little salt and pepper to taste.
Serve the halibut with the samphire or asparagus, along with the tarragon beurre blanc.
Cook’s tip: Use wild Alaska salmon or Pacific cod instead – with or without the tarragon in the sauce. If you can’t find samphire, substitute with asparagus.
• 25g (1oz) butter
• 1 tbsp olive oil
• 4 x 150-200g (6-7oz) fillets wild Alaska halibut
• 300g (10oz) samphire or asparagus
For the tarragon beurre blanc:
• 2 shallots or 1 very small onion, very finely chopped
• 2 tbsp white wine vinegar
• 4 tbsp dry white wine
• 2 tbsp double cream
• 150g (6oz) chilled unsalted butter, diced
• 1 tbsp tarragon, chopped
• Salt and ground white pepper