• 6 very fresh mackerel
• 1.1 litres water
• 1 teaspoon salt

Bretonne Sauce

• 2 egg yolks, preferably free-range
• 1 teaspoon French mustard (we use Maille mustard with green herbs)
• 2 tablespoons mixed finely chopped chives
• fennel, parsley and thyme
• 170 g butter

First make the Bretonne sauce. Whisk the egg yolks in a bowl with the mustard and finely chopped herbs. Bring the butter to the boil and pour it in a steady stream on to the egg yolks, whisking continuously until the sauce thickens to a light coating consistency like a Hollandaise. Keep warm in a flask, or place in a pottery or plastic bowl (not stainless steel), in a saucepan of hot but not boiling water.

Cut the heads off the mackerel, gut and clean but keep whole. Bring water to the boil and add salt and the mackerel. Bring back to boiling point, cover and remove from the heat.

After about 5–8 minutes, check to see whether the fish are cooked. The flesh should lift off the bone. Remove the mackerel on to a plate, scrape off the skin and carefully lift the fillets off the bones and on to a serving plate. Coat carefully with warm sauce. Serve with a good green salad and perhaps some new potatoes.