8 x 75 g (3 oz) mackerel fillets
Mint sprigs, to garnish
For the Sauce:
2 tablespoons sherry vinegar
1 shallot, very finely chopped
2 tablespoons cold water
2 egg yolks
225 g (8 oz) Clarified butter
1 teaspoon lemon juice
A good pinch of cayenne pepper
1 tablespoon chopped mint
Salt and freshly ground black pepper
First make the sauce. Put the sherry vinegar and shallot in a small pan and bring to the boil. Boil until reduced to about 1 teaspoon. Half-fill a pan with water and bring to the boil, then reduce to a simmer and rest a glass or stainless-steel bowl on top. Put the water, egg yolks and sherry vinegar reduction into the bowl and whisk vigorously until voluminous and fluffy.
Remove the bowl from the heat and gradually whisk in the clarified butter, building up an emulsion as if making mayonnaise. Add the lemon juice, cayenne pepper, chopped mint, ½ teaspoon of salt and some black pepper. Set aside and keep warm in a bowl of warm water.
Bring 1.2 litres (2 pints) of water and 2 tablespoons of salt to the boil in a large clean frying pan. Reduce to a simmer, add the mackerel fillets and poach for 3 minutes, turning them over halfway through cooking. Lift out, drain away the excess water and put 2 mackerel on to each warmed plate. Spoon a little of the sauce over and the rest around the fish and garnish with sprigs of fresh mint.
Place the butter in a small pan and leave it over a very low heat unit lit has melted. Then skim off any scum from the surface and pour off the clear (clarified) butter into a bowl, leaving behind the milky white solids that will have settled on the bottom of the pan.