In the UK we're fans of green asparagus, but in Germany they can't get enough of the white variety, it seems. Emma Allen set off for the Schlosshotel Bühlerhöhe to find out more
No longer seen as an "upper-class" vegetable, asparagus, despite its short growing season, has become widely available in the past few years. But white asparagus is still a novelty in the UK: most people are more familiar with the home-grown, green variety. Consumers in France and the USA also tend to favour green over white.
Elsewhere in Europe, though, it's white asparagus that is the most popular. In Germany, the white stalks are a highly prized delicacy and considered far superior in flavour to green, which is rarely eaten and used more often as a garnish.
So what's the difference? Aside from colour, green asparagus has a slightly nuttier flavour the white variety has a milder, almost sweet taste and requires peeling before cooking. And while delicate, slender stems tend to be a measure of quality in the UK, the opposite is generally true with white asparagus, with fatter, chunkier spears usually more highly rated.
The other main distinction is the way green and white plants are cultivated. Often the two types are actually the same variety, but green asparagus is grown above ground, in sunlight, while white is grown in deep mounds of soil to protect it from the chlorophyll-inducing sun, meaning the vegetable keeps its pale, creamy colour. Harvest, when spears are cut by hand with a special knife to avoid stalk damage, has to be quick to stop discolouration - and a resulting drop in value. In high season, with warm weather, farms will often harvest twice a day as growth is so rapid, with stems turning green in as little as two to three hours.
The biggest white asparagus producer in Europe, with an industry worth €250m (£169m) a year, Germany takes asparagus (or "spargle"), very seriously. The season - usually from the beginning of April until around the third week of June, depending on the weather - is deliberately kept short to give plants plenty of time to regenerate for the following year. Regulations on what makes the grade - or not - are also strict.
Plump, firm stems with a velvety sheen are the ones to look for, according to the OGA, a fruit and vegetable co-operative in Bruchsal, near Baden Baden in southern Germany, which produces almost half the country's white asparagus crop. Grading is more important than variety or terroir, and even though different regions claim their produce is the highest quality, it's the spears' classification that counts.
Top-quality (or Class I) white asparagus must be pure white, have closed tips and be absolutely straight, with only a very little colour or "rust" allowed on the stem. Class II, often bought by restaurants as it's about €2 (£1.35) per kg cheaper than Class I and still of a high quality, allows a slight curve and a little opening of the tips. Measurements, too, are precise, with stems between 16mm and 26mm in width fetching the highest prices. Generally, the best time to buy is in May, the peak season, when prices can drop to half those in early April.
At the five-star Schlosshotel Bühlerhöhe near Baden Baden, close to one of the region's main asparagus growing areas, Michelin-starred chef Christian Scharrer devises a special weekly-changing white asparagus menu each season and is a firm fan of white over green. "The taste is much more distinctive and if you're a creative chef, there are no limits to what you can do with it, whether you grill it, barbecue it, use it in soups, gratins soufflés or risottos," he says.
For best results, Scharrer advises gently boiling white asparagus in water with some salt, an equal amount of sugar and the juice of half a lemon (to stop it from discolouring). Depending on thickness, he says, seven minutes or so is about right for al dente, or up to 10 minutes for more tender stems. "White asparagus, being more porous than green, can quickly lose texture and become soggy so you have to be careful not to overcook it," he adds. "Make sure you peel enough off to get rid of any woodiness and if you find it's too bitter, add a slice of bread to the pan."
Scharrer advises against refreshing cooked white asparagus with cold water - "because it will lose flavour." Instead, leave asparagus to cool in the cooking liquor for a sweet, intense taste.
Storage is also important. Left in warm surroundings, white asparagus will dry out and can turn sour, so the best method is to keep it refrigerated, wrapped in a damp cloth to retain moisture. Stored this way, asparagus should easily keep for four to five days.
In Germany, the traditional way to serve the vegetable is with Black Forest-cured ham, boiled new potatoes and hollandaise sauce. This is still the most popular, although chefs such as Scharrer are turning to more unusual cooking techniques or innovative combinations.
On his current menu is a starter of marinated asparagus with caviar and fried langoustine and a main course of poached fillet of veal, with salsa verde, asparagus and gnocchi. Other dishes include slow-cooked salmon with Baccalau mousse on asparagus and baked asparagus with poached oysters. He is also fond of using rich ingredients to bring out flavour. "Morels have just come into season and they work beautifully, as do black truffles," he says. One recent dish he has experimented with is asparagus ravioli, using eggs rather than pasta by cooking the eggs in a bain-marie at 63°C for 90 minutes. This gives the eggs a soft, cream-like texture that can be rolled out like a pasta dough to make ravioli parcels.
Henri Brosi, head chef at the Dorchester, in London, is another white asparagus fan. He prefers white to green as he thinks the flavour is less bitter. He serves it (when it is in season) in starters, main courses or simply as a side option. "It can be used for a range of dishes," he explains. "It is great served cold in a salad with a simple vinaigrette, or warm with scallops, with veal and it works particularly well with fish such as sea bass."
For German-born Bernhard Mayer, executive chef at the Four Seasons hotel in London, currently preparing his annual white asparagus menu (running from 14 May to 8 June), white asparagus also works well with sweeter flavours. One of his biggest-sellers last year, also on this year's menu, was a white asparagus risotto, served with pan-fried sea bass fillet and strawberries, chilled and poached in vanilla. "It's a lovely sweet and savoury mix, with delicate vanilla ideally suited to the natural sweetness of the asparagus," he enthuses. He also recommends pairing same-season fruit, such as strawberries and rhubarb and adds that chocolate can work well, too, with his menu featuring a dessert of white asparagus and Valhrona chocolate tiramisù, served with rhubarb compote.
However, white asparagus is still difficult to get hold of in the UK, which means it's likely to remain a specialist product, at least for now. Victor Aveling, chairman of the British Asparagus Growers Association, says it is highly unusual for growers to cultivate the white type here because of a perceived lack of demand from consumers and caterers, though this could easily change with increased consumer awareness. At the moment, what tends to be more readily available is imported white asparagus from Greece and Bulgaria, which can cost up to half the price of the German variety. However, Aveling says, this asparagus can be inferior in taste and quality, lacking the sweetness of the German product. For that reason, Mayer says, he prefers to source his asparagus directly from the Baden Baden region, although he points out that he would be willing to try any UK-grown varieties if available.
Mayer says he is surprised at how little white asparagus is used in the UK and feels there is a market for it. "I first did a white asparagus menu five years ago and since then, demand has increased as more people try it," he explains. He doesn't think the white variety is a particularly difficult sell, even though the slim-stemmed green English asparagus is so highly rated here. "When we're running the special menu, I'd say 70% of our diners choose white asparagus dishes," he says. "Americans are probably the most reluctant because they tend to love green. But once they've tried it, they usually like it."
White asparagus can be grown from the same variety as green - the difference is that white is grown in deep soil (above), protecting it from the sun. It is harvested by hand with a special knife that avoids stalk damage (below), and harvesting has to be quick to stop discolouration. At peak season, farms will often harvest twice a day (right) as growth is so rapid. The precise grading system applies to size as well as to colour and condition: stems between 16mm and 26mm in diameter (below, right) fetch the best prices
All white now
Wholesale veg importer and distributor 4°C will stock German white asparagus from May as part of a trial promotion with contract caterer Charlton House. Mike Smith, the company's executive chef at City-based SJ Berwin, has developed the recipes shown here. For details of where to buy white asparagus in the UK, contact Richard Perton at 4°C on 020 8558 9708, or visit www.4degreesc.com, or CMA, the German Agricultural Marketing Board, on 020 8944 0484 or visit www.germanfoods.co.uk.