A distant relative of its globe namesake, the Jerusalem artichoke is often overlooked, but in the hands of a Michelin-starred chef such as Matthew Tomkinson this inexpensive tuber finds many uses. Michael Raffael reports
In size, shape and look, Jerusalem artichokes have much in common with Ratte or Pink Fir Apple potatoes. They are tubers too, grown underground. Like potatoes they came to Europe from America - some authorities say Brazil, others Peru and still others North America. They are only a very distant plant relative of the globe artichoke.
After a honeymoon period 300 years ago, when they were valued, they were pushed to the fringes of kitchen gardens. In Britain, their distinctive, sweetish taste fitted them for the role of supporting vegetable accompaniment. They were less colourful than carrots, beetroot or swedes, and they were harder to peel than parsnips. French cooks were quite sniffy about "les topinambours" because peasants grew them as a crop for animal fodder.
Too many chefs they have been an unknown quantity: they aren't reviving an ingredient that goes in and out of fashion so much as discovering something new. With this fresh approach come parallel challenges. How does a chef integrate this peculiar vegetable into a dish that works? How does he adapt the techniques at his fingertips to suit it?
The short answer to the second question is that anything goes. Raw, pickled, mashed or deep-fried Jerusalem artichokes can be anything from a background flavour on a plate to the focus of a dish. At the Montagu Arms hotel in the New Forest, whose Terrace restaurant holds a Michelin star, chef Matthew Tomkinson is constantly looking for new ways to present them. They grow in the hotel garden and cost him nothing.
DIGESTING JERUSALEM ARTICHOKES
Perhaps Jerusalem artichokes would have remained more popular were it not for their reputation for causing flatulence. In basic scientific terms, they contain a kind of dietary fibre that enzymes in the human body can't digest. Instead, bacteria in the gut take over this role, but produce carbon dioxide, too.
In the kinds of preparation and quantities served by restaurants such as the Montagu Arms, the side-effects aren't so noticeable. They are allegedly worse when artichokes are boiled in water; less when eaten raw.
When puréeing a batch of artichokes the moisture content can vary. If it seems necessary, add a small splash of cream.
For service, keep the purée in a squeezy bottle in the bain-marie.
Respect the 160ºC temperature for frying to prevent the crisps becoming bitter.
When baked (eg, in a salt crust) the texture becomes mushy and hard to handle.
To keep the line-caught bass flat when frying it, put two or three stacked side-plates on top of it.
Don't fuss overmuch about colour. Anything from off-white to pale grey is good.
Gardeners consider January to March to be the high season, but it stretches into the spring and starts in autumn. Unlike some root crops, it's better to leave the tubers in the ground until they're needed. Once dug up, they store for several weeks. During this time they become softer and harder to peel, but there's little change to the taste.
PREPARATION AND BASIC METHODS A Jerusalem artichoke's skin is thinner than a main-crop potato's, and recipes for the general public often say that peeling is unnecessary. In a bistro or pub-grub context this guideline may be valid; it will also give a more earthy flavour. However, for fine dining, peeling is a smart option. The larger the tubers, the less waste there will be.
If they are fresh out of the ground, scrub them under running water to remove all soil. Peel them and start to process them straight away.
Note: After peeling, the artichokes will quickly start to discolour if left. Older recipes suggested either rubbing with lemon juice or boiling them in a blanc (water with a little flour whisked in) to retain their whiteness. Neither method is necessary or helpful.
WATER BATH (FOR PUREE) The artichoke's texture lends itself to poaching in a water bath.
Slice the peeled tubers to the thickness of a 50p coin. Pack them into a medium-sized vac-pack bag (between 400g and 500g). Spread them so they are flattish and seal under vacuum. DonÕt add any salt at this stage.
Poach them for approximately one hour at 85ºC until they are soft.
For a purée, blend in a Vita-Prep or similar blender and then season.
PICKLE The texture of raw Jerusalem artichoke is similar to a water chestnut's or fresh ginger root. It lends itself to pickling. At the Montagu Arms, Tomkinson uses a 50/50 uncooked water-wine vinegar pickle flavoured with sugar, salt, thyme and garlic.
Slice the peeled artichoke finely on a Japanese mandolin. Pack the slices loosely in a vac-pack bag. Add about 150ml pickle per sachet and seal. Store, refrigerated, for 48 hours or until needed.
CRISPS Because Jerusalem artichokes contain about 10% sugar (carrots have about 5%), they discolour rapidly if deep-fried at high temperatures.
To make crisps, heat the deep-fat fryer to 160¡C. Slice the artichokes on a Japanese mandolin so they are almost transparent.
Fry the slices a few at a time until they are lightly coloured. Drain on absorbent paper or a cloth (carry-over heat will allow them to turn golden). Store in a sealed container until needed.
SOUP When blended, the artichokes have the texture of a fine velouté (velvety) soup without the addition of extra cream.
Sliced fine and sweated in oil or butter, they soften more quickly than potato. It would be possible to prepare a portion of soup to order by sweating 100-120g peeled and sliced artichokes in 20g butter or 20ml oil, adding 100ml of semi-skimmed milk, 100ml vegetable stock and seasoning. Simmer until the vegetable is soft
(or leave in a very cool oven) and blend.
A batch of the soup can be scaled up using the above proportions as a guideline.
CREAM Tomkinson makes a savoury bavarois as an amuse-bouche by folding a mixture of whipped, whipping and double cream plus gelatine into a seasoned artichoke purée.
SAUTE Like potatoes, artichokes can be sautéd from raw or part-cooked and then finished in the pan.
COST Expect to pay less than £3 per kg.
According to Tomkinson: "Jerusalem artichokes grow in the Montagu Arms garden, and we realised that unless we were proactive and started using them weÕd be wasting a natural resource."
This means, effectively, that if he has 60 covers booked, he can offer 60 amuse-bouches (see Jerusalem artichoke cream below) at a negligible cost.
His kitchens aim to run a 74% gross profit. To make this margin he is dependent on the produce that's available in-house.
|FILLET OF LINE-CAUGHT WILD SEA BASS, SAUTED GLOBE ARTICHOKES, DORSET WATERCRESS AND HOME-CURED HAM The Jerusalem artichoke purée acts as a bed for bass fillet served with artichoke bottoms, in-house dried tomato, cress and ham (which is cured in the kitchens for 18 months or longer using New Forest pork).|
|JERUSALEM ARTICHOKE GRATIN Slices of artichoke are left to infuse in milk and cream with rosemary on top of the range ahead of service. Each portion, offered as a vegetable accompaniment, is spooned into a miniature copper pan topped with Parmesan and chives and then gratinated.|
|JERUSALEM ARTICHOKE CREAM WITH PICKLED MUSHROOMS AND ARTICHOKE CRISPS Offered in a shot glass or a miniature ceramic bowl, it's a regular taster on the £65 la carte menu.|
|ROASTED SCALLOP WITH JERUSALEM ARTICHOKES, ROASTED LEMON PUREE AND BROWN BUTTER A spoonful of crushed baked artichoke accompanies a single scallop, fried in clarified butter with a touch of garlic, and a cube of cured pork belly plus a dab of roasted lemon and beurre noisette.|
|ROAST CAPON WITH SALT-BAKED ARTICHOKES, SPINACH, CHICORY AND SWEET SHALLOTS Salt-baked Jerusalem artichokes have a more concentrated flavour than those either simmered in milk or poached in a water bath. Lightly crushed, they hold their own against other powerfully flavoured ingredients that make up the dish (genuine capon has a more pronounced poultry flavour than chicken).|
|JERUSALEM ARTICHOKE SOUP WITH CEPS This used to be popular as "Palestine soup". In the picture, the velouté soup is served with ceps and olive oil and a crožte topped with purée and pickled enoki mushrooms. As an alternative, chef might use wild mushroom tortellini.|