What is really surprising about this recipe is that a simple mixture of the fish juices, a bit of oil, a few herbs, some cream and some water, produces such a sophisticated sauce. It’s also a unique way of cooking fish, somewhere between braising in a sauce, and baking. Plus you have the bonus of the crunchy topping, a lawn of deeply satisfying zesty green loveliness. We rarely serve this with anything more than some steamed spinach or pak choi. If you have any of the topping left over, bung it back in the freezer for next time. You’ll need a baking tray that’s only slightly larger than the fish, and isn’t too deep.

1 cod, about 1.2kg, filleted, skin on. (We’ve done it with whiting too, and that was lovely).

1 tbsp coarse grain mustard

Crust:-

200g unsalted butter

200g good-quality white breadcrumbs, not too fine

100g curly-Ieaf parsley leaves (3 to 4 tbsps)

grated zest of 2 lemons

Tomato sauce:-

3 tomatoes, skinned, seeded and finely chopped

3 tbsps olive oil

Sauce for fish:-

1 bay leaf

2 tbsps dry white wine

2 sprigs fresh thyme

3 tbsps double cream

sea salt and freshly ground black pepper

300ml Water

Half glass dry white wine

• Blend the butter and crumbs in a food processor until crumbly. Drop in the parsley, lemon zest and seasoning, and whiz to fine crumbs. Line a wooden board with cling film and tip the buttery crumb mixture on top. Cover with more cling film, and roll out with a rolling pin to a rectangle about one centimetre thick. Place this crust on a plate in the freezer to firm up for a couple of hours

• Check the fish fillets for any pinbones, then cut each across in four to make 8 pieces – we’ve found it easier to do 8 small pieces, 2 per person, than 4 larger ones. Set aside

• Cook the chopped tomato in 1 tbsp of the olive oil for 5 to 8 minutes until you have a slightly chunky purée. Season and set aside

• When ready to cook, preheat the oven to 200°C, Gas 6

• Thinly spread half of the mustard over the skin of the fish, then place, skin side down, in your baking tray

• Then carefully spoon the tomato purée onto the fish pieces. Finally, take the parsley crusts out of the freezer, cut into pieces about the same size as your fish fillets, and press one gently on top of the tomato sauce. You can use smaller bits to fill in around the edges. Set aside whilst doing the following

• Put the remaining 2 tablespoons of oil in a small saucepan with about 300ml of water, the wine, the herbs and seasoning. Bring to the boil. Carefully pour the liquid down the side of the baking dish so it doesn't wet the crust. Put in the oven and bake, uncovered, for 10 minutes until the crust is light and crisp and the fish feels firm when pressed lightly in the centre. Remove from the heat and, using a long spatula, lift out the fish carefully onto four warmed dinner plates. (We usually place it on top of the cooked spinach/pak choi)

• Place the baking dish on the hob, or (pour it off into a saucepan), add the wine, and boil down the liquid by half, then add the remaining mustard and the cream, and whisk till smooth. Pour neatly around the fish and serve