This week, as a bit of a change, something a little more cheffy than usual. I occasionally like to flex my culinary muscles, and this week I’m doing just that with a fish dish that uses one of the classic French culinary sauces, the wonderful beurre blanc.

A smooth, tangy emulsion of butter, vinegar and wine, it’s rather fallen out of favour these days, probably on health grounds, given the rather large amount of butter required.

This is a bit of a shame, as it’s one of the nicest sauces for accompanying fish and shellfish, and is fairly easy to make, compared to its

trickier cousin, the Hollandaise.

Originating in the Loire, it’s said that beurre blanc was one of those happy kitchen accidents that result in legendary recipes, where the chef had planned to make a Béarnaise sauce but had run out of tarragon and instead made the simple egg-less butter sauce we know today.

The beurre blanc forms the base of our sauce, known as Beurre Cancalaise, which is peppered with finely-diced vegetables, herbs and citrus zest, to make a tangy, flavourful accompaniment to our firm white fish.

The recipe, I’m presuming, originated in Cancale, the delightful seaside town in Brittany (where, incidentally, I once ate the biggest oyster I’ve ever seen; like a dinner plate, it was!) combining root vegetables grown in the rich local soils, along with tangy apple (North-West France is famous for its cider) and some piquant garden herbs.

Cancale in Brittany

Cancale being one of France’s earliest trading ports, the region took to using rare ingredients with ease – spicy gingerbread originated in the area, apparently – and citrus fruits fresh off the boats from the tropics were swiftly combined with the abundant local seafood and a marriage made in heaven was created.

Hence the appearance of the two zests in this recipe, adding their sweet perfume to the dish just as it’s served.

There’s a fair bit of fiddly preparatory knife-work here, but it’s really worth the effort, and a lot of the preparation can be done well in advance.

The pomme purée, for instance, can be made a day or so beforehand and simply reheated. And this base sauce is so versatile, it’ll even go with roast chicken pieces or even a nice grilled pork chop, though it really is at its best with some firm fillets of white fish, sizzled scallops or a big juicy lobster, should you really fancy (forgive the pun) pushing the boat out.

Serves 4

For the fish:

8 fresh sole fillets, or other firm white fish (turbot, plaice, halibut)

A little plain flour

A little butter

For the Cancalaise vegetables:

A small leek, very finely diced

Small white turnip, very finely diced

4 radishes, very finely diced

1 small carrot, very finely diced

¼ bulb fennel, very finely diced

1 banana shallot, very finely diced

6 button mushrooms, very finely diced

A Granny Smith apple, peeled and very finely diced

A few chives

A small sprig of fresh dill

Grated zest of 1 orange

Grated zest of 1 lemon

For the Beurre Blanc:

1 banana shallot, finely minced

60ml white wine vinegar

60ml Noilly Prat vermouth or dry white wine

Noilly Prat

125g/4½oz chilled unsalted butter, cut into small chunks

A little Maldon salt

For the pomme purée:

1 kg baking potatoes

100g unsalted butter, melted

100ml double cream

Maldon salt and freshly-ground white pepper

Method:

First, prepare the pomme purée; peel the potatoes and dice into equal-sized chunks. Bring a large pan of salted water to the boil and cook the potatoes until the point of a knife will go through each chunk with ease. Drain the potato and allow it to steam dry. Then, pass through a mouli or mash by hand into a clean pan. In a separate pan, heat the butter and cream until bubbling, then fold into the mashed potato. Check the seasoning and set aside until you’re ready to serve.

Next, prepare the Cancalaise vegetables; heat a clean pan of water with a little salt. When boiling, blanch each vegetable, plus the mushrooms, separately for 30 seconds, plunging each batch into ice-cold water when cooked.

Dry the vegetables on a teatowel, and refrigerate until required.

To make the beurre blanc, put the shallot into a medium-sized saucepan and add the vinegar and vermouth, then heat until the liquid has reduced to about a third of its original volume. Whisk in the pieces of butter one at a time, making sure each piece melts and emulsifies before adding the next. Careful not to boil the sauce lest it split. I tend to alternate the pan over the heat and off the heat as I add the butter and whisk quickly.

Eventually, you should have a stable, creamy, smooth sauce. Add the vegetables, along with the apple, the chopped herbs and the zests.

Check the seasoning and keep the sauce warm as you finish the fish. Dredge the sole fillets in plain flour and pat away the excess. Heat a small amount of butter in a frying pan, and, when foamy, add the fish fillets, cooking for a couple of minutes on each side.

Serve on top of a good dollop of pomme purée and spoon plenty of the Cancalaise butter sauce around.