Pickled walnuts: we’re crackers for this ancient British delicacy

Len Goodman, the retired Strictly Come Dancing judge, loves a pickled walnut, and so do I. But, no doubt about it, they are a curious thing. Blackish brown and the size of a marble with flattened poles, flaking skin glistening with vinegar, a pickled walnut looks more like something you’d find washed up on a windswept beach than a foodstuff. Slice into the tender flesh and the strange curling markings inside reinforce this impression of a rare sea vegetable.

Gastronomically, it bears little relation to the hard-shelled walnuts on the Christmas table, or those crinkly bifurcated nuts that decorate the fruit cake or jostle with celery and apple in a Waldorf salad. Sweet and sour, with a faint woody flavour and juicy, soft texture, they are excellent companions to the British tradition of cold meats and cheese – not to mention Christmas leftovers – and have been for centuries. Dorothy Hartley in her classic book Food in England lists an 18th-century recipe for pickling walnuts, as well as a 14th-century fish recipe with a pickled walnut sauce.

Delia sparked a renaissance with that dark, rich venison, Guinness and pickled walnut casserole in her Christmas cookbook. These days, you’ll find them on the menu at London restaurant St John, with potted beef and green beans, at Soho’s Quo Vadis with bavette, horseradish and watercress or at Bristol’s Wallfish, served in a salad with beetroot and ricotta. They are also being championed by food writers such as Yotam Ottolenghi, Gizzi Erskine and Kay Plunkett-Hogge.

Surprising, then, that there is just one commercial producer of pickled walnuts left in the UK, the family company Opies based in Kent. As William Opie, the grandson of the founder, explained to me, the company was set up in the 1880s by a Cornish tin miner, Bennett Opie, who took advantage of the newly opened railway line to ferry fresh eggs from the West Country into London. The business now concentrates on an array of preserves, including ginger in syrup and those bright red cherries in syrup that dangle on the edge of camp cocktail glasses.

It was only in the Sixties, when a local producer of pickled walnuts closed its doors, that Opies took up that baton. By then Britain’s once-thriving walnut industry had almost disappeared, and most of the walnuts that Opies uses are imported from France and Italy. But Opie is on a mission to increase the number of British nuts that the company uses. A chance meeting with farmer John Leigh-Pemberton (son of the former Governor of the Bank of England, Robin Leigh-Pemberton) led to Leigh-Pemberton planting a grove of 500 trees at his farm near the Opie factory in Sittingbourne, Kent.

Walnut farmer John pictured in his local orchard which supplies Opies with about 1% of their walnuts Credit: Julian Andrews

During last summer’s late-July heatwave, I visited the farm with Opie to see the walnut harvest. The grove was an English idyll, butterflies flitting past the trees, while the farm’s sheep grazed underneath.

Pickled walnuts are made from the green walnut fruit, before the woody shell has started to form inside. Leigh-Pemberton picked one of the emerald-green golf balls and cut it open. Under the waxy, bright-emerald skin, the flesh was white as a Granny Smith, with just the suggestion of the creamy crinkle in the centre, indicating the embryonic nut. Getting the walnut fruit at the right point is tricky, he explained. “Every day for about two weeks I cut one open and as soon I find the tiniest hint of brown line – the young shell – I pick them all straight away.”

These walnuts were ready, and the picker Olga Bubulici arrived with a “kibsie”, a huge basket strapped to her waist. Scaling a tripod ladder, she started filling the kibsie with green nuts. All the picking is done by hand.

Some trees on the edge of Leigh-Pemberton’s grove are left unpicked for the Bubulici family, who travel from Moldova to help with the harvest. In August, when they gather the plums from the trees in the next field, at lunchtime they picnic under the walnut trees, cut open the green husk and scoop out the soft walnut within. “At home we would make a jam with the green walnuts,” said Olga.

The walnuts are then tipped into barrels, which are topped up with a mix of water, acetic acid and salt, to begin the pickling process. In a week or so, they have turned from green to the familiar black. Next they are steamed for 10 minutes, before being tipped into vats of water to soak for up to two weeks. The long soaking time is an important part of the recipe, adapted from a Victorian method by William’s brother, Philip Opie, the former chairman at Opies, now retired. It ensures that all the bitter tannins are removed, said Opie. “In the early days they were a bit too tannic, then we got it right and the sales just soared.”

Factory workers 'topping and tailing' the walnuts Credit: Julian Andrews

We visited the Opies production rooms to see the walnuts being hand trimmed. From next door came a waft of lemon scent, as four white-hatted women stacked lemons on a slicing machine ready for the bar tenders’ jars of lemon slices, while further on – in huge tanks – the cherries were macerating in sugar syrup for the maraschino cherries. But here in the walnut room, the tops and bottoms were being sliced off each nut to check that there was no trace of hard shell inside.

It’s as much a matter of feel as sight, explained one of the trimmers. “There’s a telltale resistance to the knife when there’s too much shell.”

More than 10 per cent of the nuts will be rejected before they are packed by hand into jars. In goes vinegar and the secret ingredients – spices and a bit of sugar – before a final pasteurisation to give them a three-year shelf life.

“They really need two or three months in the jar for the spices really to go in. You have to get ahead, like with Christmas puddings,” said William. Well, pickle my walnuts, as Len would say. Good thing they’ve done it for us.

Roasted porcini with burrata and pickled walnuts

When we consider indulgent food we tend to imagine meat or seafood, but some of the most decadent of all grow right out of the ground. Porcini mushrooms or ceps (whichever you want to call them) are the king of mushrooms.

They have a short season and are few and far between, so can be quite pricey, but for their meaty, dirty, fragrant flavour it’s worth it. Pan-roasting a few of these in garlic and parsley to just serve simply on a plate is a joy; to make them a bit more “fancy”, serve your porcini at room temperature, adding some pickled walnuts and a heaving ball of oozing burrata cheese to scoop on to garlic butter croutes as a starter, canapé or part of a buffet.

SERVES

6-8 as a starter or as part of a buffet

INGREDIENTS

3 tbsp unsalted butter
3 tbsp good olive oil
700g nice big fresh porcini mushrooms, cleaned and trimmed, each sliced into 4 along the stalk
2–3 garlic cloves, very finely chopped
2 tbsp finely chopped flat-leaf parsley leaves
3–4 pickled walnuts, roughly chopped
3 small balls of burrata, left to get to room temperature, drained and dried with kitchen paper
Really good extra virgin olive oil, for finishing Micro parsley or flat leaf parsley, to garnish

METHOD

Heat the butter and oil in a very large frying pan. When the pan is roasting hot and the butter is foaming, add the mushrooms in batches and fry until heavily bronzed. When they’re all done, put them back into the pan along with any juices (they should all fit now they’ve been cooked and lost their water content), add the garlic, stir in the parsley and season heavily with salt and pepper.
Lay on a serving platter and leave to get to room temperature, which doesn’t actually take that long.
Sprinkle over the chopped walnuts and, if you like a little more zing, 1tbsp of the vinegar they’ve been pickled in. Add the balls of burrata to the platter – you can keep them whole or tear into them a bit.
Season with more salt and pepper, garnish with parsley and drizzle with good olive oil to serve.

From Gizzi’s Season’s Eatings, by Gizzi Erskine (£25, Mitchell Beazley)