Silla Bjerrum, Danish-born owner of London restaurant Feng Sushi, has travelled to the island of Bornholm in Denmark to discover how to unite sushi, herring marinades and MSC-certified fish. Hannah Thompson went along for the ride
Silla Bjerrum is just one false step away from falling into the Baltic Sea. The wide sheet of slate-grey ocean throws dense, white foam over Bjerrum's shoulders and swirls in circles around the waders that come all the way up to her chest.
Although she is holding two silvery herring, she isn't fishing. That's already been done. Just a few steps away, a tonne of filleted Danish herring has just been sorted into barrels and brined and sealed, ready for marinating three weeks later. Such is the work of the ChristiansøPigens herring factory on the Danish island of Bornholm and its owner Kim Rømer.
Originally from Copenhagen, Bjerrum came to London in the early 1990s. It was while working in a Japanese restaurant that she fell in love with Eastern cuisine and opened Feng Sushi as a delivery restaurant in Fulham in 1999.
The Feng Sushi group now runs to nine restaurants and delivery centres across the capital, with the bulk of the trade coming in via online orders. The menu is created by highly-trained chefs (who often go on to work at places such as Nobu and Zuma) and includes a rich and varied array of hand-crafted sushi and fish, including king prawn tempura, hand-dived scallop maki and hake udon soup.
But this isn't just any old fish. As a chef, Bjerrum cares about the produce her shops use and she has long been a champion of sustainable fishing. She is a proponent of the Marine Stewardship Council (MSC) certification and also works to ensure that all her fish and seafood is sustainable. The restaurants' mackerel, prawns, hake and ikura (roe) are already there; next stop, herring.
Hence the Baltic Sea. We're travelling round the island on a taste adventure to discover if the strong, aromatic flavours of Bornholm herring might work with the delicate rice beds of Japanese nigiri. And, if so, how this might be achieved in the most sustainable way.
We first visit RÁ¸mer of the herring marinade factory ChristiansÁ¸Pigens. It's no industrial plant: from outside, it could pass for a normal house, albeit a very rural one, perched on the road next to the rolling sea.
Inside, however, it's all stainless steel, white aprons and boxes of fish. A woman in a white cap sorts the fillets - which at this stage are soft but fairly tasteless - into a collection of large plastic barrels grouped all around us like an expectant audience.
Tall and talkative factory owner RÁ¸mer exudes confidence, nimbly mixing the white herring fillets in their barrels to make sure they all have an even covering of brine before sealing them. The factory only processes around 25 to 30 tonnes a year - and supplies three Michelin-starred restaurants in Copenhagen - so this one tonne marks a large haul.
Three weeks later the fish emerge, tenderised by brine, ready to be marinated. Around the corner, another white-capped woman stands in a bright room, placing fillets into small branded pots. Calm and methodical, she trims the fish before layering them with care and covering them with a mystery spice mix. It's red and pungent, and we try to guess: paprika? Chilli? Five spice? They'll never reveal the recipe. Factory owner RÁ¸mer paid 1m kroner (£106,300) for the secret and it's more than his job is worth to let it go. And yet, we try again: juniper? Lemon? Sugar, vinegar, salt and cloves, that's for sure.
We are given different marinated herring to try: one with tomato, one with curry, one with a "light" marinade and one that's richer and super-strong. Each packs a powerful punch - a tangy hit of vinegar and deeply blended spice plus a lingering touch of sweetness.
Next, it's a visit to another producer, Rikke Hansen, whose family herring business was started by her grandmother Ruth on the tiny island of ChristiansÁ¸ in the Ertholmene archipelago. It's 30 miles away and the place is so minuscule that on a normal map it looks like nothing more than a fleck; a printing error.
ChristiansÁ¸ (named for old King Christian V) is an unlikely tourist destination. It has just 100 residents, no cars or pets, a smattering of saffron-coloured buildings and, in low season, a ferry less than once a day, and yet still they come - around 40,000 visitors a year - to taste Ruth's famous herring.
This recipe is also a secret, and the packaging mentions just sugar, vinegar, salt and "spices" - the minimum label information that Danish law demands. And therein lies the rub: although apparently identical to Kim's, it's actually pretty different - smoother, more subtle. Nevertheless, Bjerrum reckons it's still too strong for sushi.
"You can't just take the current herring recipes and put them straight on rice as they are - they're too harsh and salty," she says. She explains that she prefers to cure fish for just hours at most to achieve a more refined texture and flavour. But then she adds: "I'm thinking I could make a marinade with kombo (seaweed), shiso (Asian herb), and maybe some nori (red algae seaweed)â¦"
And the inspiration keeps coming. As Bjerrum chats to Hansen over the kitchen table, it's clear that the trip has sparked her creativity. We walk to the seafront to see where Hansen's partner fishes for herring and the pair keep talking a mile a minute in lyrically-punctuated Danish - discussing techniques, marinating time, flavours, spices and sourcing.
We plan to take home as many tubs of herring - from both RÁ¸mer and Hansen - as our luggage restriction allows, but Bjerrum takes a whole box and more, collecting 14 different flavours to taste and try, bound for her Feng Sushi development kitchen back in west London's RavensÂcourt Park.
And then, although we're 600 miles from home, the Baltic Sea moving all around us and the taste of strong Danish herring on our tongues, that sushi kitchen in urban London - with its miso, yuzu, dashi, wasabi, soy and mizuna - suddenly doesn't seem all that far.
The MSC and herring
Marine Stewardship Council-certified herring in the UK is landed in Hastings, and it is this fish that Bjerrum will use in her Feng Sushi kitchens.
2005 The Hastings fishery is first certified as MSC.
2012 Hastings is re-certified as MSC to ensure the standard is being maintained.
10 tonnes The annual MSC-certified catch in Hastings.
987,952 tonnes The annual volume of MSC herring in global markets.
10 metres The maximum length of the boats used.
Within 6 miles The distance limit off Hastings in which fishing takes place.
The MSC has also certified 12 other herring fisheries across Scandinavia, Ireland and the North Sea, plus two focused on the Baltic.
Sometimes fish that is landed according to MSC standards does not enter the market as MSC-labelled, because the processors or suppliers may not yet be certified. This is true of Billingsgate market in London, one of the major sources of fish to the capital.
The MSC is currently working to enable at least one supplier to achieve MSC status, thereby further improving the supply of certified sustainable fish from sea to plate.
Silla Bjerrum's Japanese herring cure
Salt the herring for an hour, then wash the salt off. Marinade the herring in a mixture of sushi vinegar, kombu and soy sauce for an hour. Pin-bone the fish and remove the skin.
"Coarse sea salt is the best," says Bjerrum. "I also like to use sushi vinegar because of the sugar. The kombu is a natural flavour enhancer and brings out the buttery-ness."
Silla Bjerrum and Feng Sushi
22 The number of years Silla Bjerrum has been based in the UK
1999 The date the first Feng Sushi opened in Fulham
9 The number of restaurants Feng Sushi now has, including in Kensington, Billingsgate, Notting Hill and Chalk Farm
7% The percentage of business that originally came from online orders
55% The percentage of online orders now
150 The number of staff across the Feng Sushi group, including trained chefs
Silla Bjerrum on herring - Japanese-style
Silla Bjerrum says that her search for Danish herring is her missing link between Japan and Denmark. Although she is dedicated to Japanese cooking, she still longs to bring elements from her native cuisine into her food.
"This was my search for the bridge between the traditional marinating process and my background," she explains. "But I needed to learn the original script before I could change it."
The main difference between Danish herring and Bjerrum's Japanese version is the curing time.
"The Bornholm herring flavour is too powerful to mix in with the Japanese flavours," says Bjerrum. "But by understanding the curing process, I devised a more delicate, Japanese version. It made me braver. I wanted to keep the fish tasting really fresh and firm without being overpowering."
Similarly, in her restaurants, Bjerrum has introduced the herring alongside mackerel dishes, so people aren't too intimidated by the new fish. There are also maki rolls, sashimi, and soba noodles (see recipe below).
She says: "People are more familiar with mackerel, so I thought that would be the best way to introduce the herring on some dishes. It does it a bit more justice. I want the world to join in on this herring adventure!"
Silla Bjerrum's herring soba noodles
1 daikon or mooli, peeled and sliced into 1cm discs
30ml soy sauce
1tbs hondashi (Japanese fish stock made from cured and smoked bonito)
1kg spinach and rocket, washed
200g dried soba noodles
8 pinboned, cured herring fillets
Salt and pepper
4 spring onions, finely chopped
Simmer the mooli, soy, mirin, hondashi, honey and 500ml water in a pan until the mooli is just soft. Blanch and drain the spinach until it is as dry as possible. Cook the soba noodles until just al dente and drain.
Add the herring to the mooli liquid and poach quickly, taking care not to break up the fish. Season and remove from heat. Pour the poaching liquid over the soba noodles and top up with boiling water.
Add the spinach, mooli and herring. Sprinkle with the spring onions and serve.
Video: discovering Danish herring
Join Silla Bjerrum in Denmark as she explains the inspiration behind her new sustainable herring recipes >>