You can do much more with fish than serve it with vegetables and potatoes or make a fish pie. A tasty gratin is much more interesting in texture and flavour, and surprisingly simple to make.
Chef Rick Stein shares his quick recipe for cod gratin in an episode of Rick Stein’s Long Weekends, in which he visits Reykjavik, Iceland. But his affinity with good-quality, fresh fish is much closer to home, specifically Padstow in Cornwall, a haven for catching cod and where Rick has focused his culinary empire. The core recipe calls for just eight ingredients and is very versatile, as Rick notes: “You can use any white fish in this gratin recipe, and you can flex your chef muscles over the béarnaise sauce.”
In a large saucepan, add butter, leeks, and carrots. Gently fry until softened and starting to caramelise.
Add the cod and flour and stir over the heat for a couple of minutes before stirring in the wine. Allow the contents of the pan to cook until thickened.
Add salt and pepper to taste, then make a start on the béarnaise sauce. Gently heat the vinegar in a saucepan then add the shallots, tarragon sprigs, bay leaf and peppercorns.
Heat gently over medium heat until the volume of liquid has reduced by at least half, then strain the liquid and set aside until cooled.
Turn the oven on to 180C/160C Fan/Gas 4 and butter a shallow ovenproof dish ready for the gratin.
Crack the egg yolks into a bowl and add a teaspoon of water to loosen. Pour the mixture into the strained, cooled vinegar, stirring as you go. Pour this liquid into a heatproof bowl set over a pan of simmering water.
Continue to whisk the mixture constantly until the sauce has increased in volume and is thick enough to coat the back of a spoon.
Melt the unsalted butter in a new saucepan on the hob. Next, remove the bowl of egg yolk and vinegar mixture from the heat and slowly pour in the melted butter in a steady stream, whisking continuously.
Keep whisking until the mixture has thickened and is smooth. Fold in the chopped tarragon and season with salt and pepper to taste.
Transfer the cod and vegetable mixture into the ovenproof dish, then pour over the béarnaise sauce and bake for 15 to 20 minutes.