Try this, says Raoul, picking up a succulent green plant from the woodland floor. We all take a leaf and eat it, making the obligatory Masterchef “mmms” and “aahs” that are used to show one is eating with intelligence. Raoul looks pleased with himself. “Ees poisonous,” he says. A psychosomatic spasm passes around the group. “But only if you eat a lot.” It is some consolation.

The occasion for such perilous grubbing is a foraging expedition in the Welsh hills, headed by Raoul van den Broucke. He is the Flemish forager-in-chief for the local gastropub, The Foxhunter, which specialises in locally sourced food and runs foraging courses to enable its customers to do the same.

Not so long ago, in the Gold Card Age, the idea of foraging for food seemed at best a charming fancy, at worst a self-indulgent folly; a Petit Hameau of food fads. Why ferret in the bushes for porcini mushrooms when you can buy them for £25 a kilo at Borough Market in Central London?

No longer. The pincer movement of rising food and falling house prices has squeezed the pleasure-seeking middle classes. We have had to turn our backs on luxury; to stop Tasting the Difference; to think twice, thrice even, before putting a packet of organic coriander into our shopping basket. We have even had to start shopping at Aldi, for heaven's sake. Clearly something must be done.

Foraging could be that something. Hunting food in hedgerows used to be confined to the sort of person who knits their own yoghurt, but the recent rehabilitation of British cooking not only sanctions but applauds such behaviour, with the chef Thomasina Miers and the forager Guy Grieve serving up spiced squirrel on Channel 4, Valentine Warner having a pop at wood pigeons and Rick Stein seasoning his fish with self-gathered wild garlic.

While such ingredients may be exclusive and recherché in gastronomic terms, they are physically abundant in the fields and hedgerows of Britain. Use these plants and you will be able to prepare meals that are not only frugal but fashionable. All you need to know is where to look for them.

Which is where courses such as this can help. The day is divided into two parts: a morning session in which you hunt and gather in hill and hedgerow and an afternoon session in which you return to the pub and feast on the fruits of your labours.

This morning, ten would-be foragers meet in front of the pub, a converted station house, at 9am. Raoul himself appears a few minutes later, wearing a wide-brimmed white hat and carrying a big wicker basket and a stick. He waves the basket in the air. “Here's some I picked earlier,” he says, pointing to some blue-grey Blewit mushrooms inside.

“In order to forage, we must first climb up this hill,” Raoul says, in a wise-old-man-of-the-woods tone. He points at the mountain behind the pub with his stick. “You know why?” The class meekly suggest answers. For the temperature? For the humidity? For the air quality? “For the pub. There's an excellent one up there.” He looks pleased.

As we walk Raoul keeps up a culinary commentary on the plants we pass. Under his expert eye a bland-looking verge becomes a salad bowl of possibilities. A single bank yields sorrel, the spicy herb “jack by the hedge” (“Excellent with lamb”) and crisp pennywort; all edible, all delicious. Rocket suddenly begins to seem as bland as iceberg lettuce.

The tastiest leaf we try is wood sorrel - the “poisonous” plant Raoul gave us initially. “It does contain poison, so you wouldn't want to eat a plate full of it. But it is fine in small quantities and an excellent garnish,” he tells us. Its taste is highly prized by local restaurants, which pay Raoul £90 a kilo for it.

The potential for poisoning adds a certain nervous edge to the morning's foraging. After all, it's not long since Nicholas Evans, the author of The Horse Whisperer, along with his wife and brother-in-law, had to have kidney dialysis after eating the mushroom Cortinarius speciosissimus. This looks like the edible chanterelle but, according to the Association of British Fungus Groups, causes your liver to “be broken down into a pulp”.

As we hunt Raoul explains some general rules for knowing which fungi are poisonous and which are safe. “Mushrooms with white gills tend to be poisonous,” he says. Someone points out that in the basket we have collected some mushrooms with white gills. “Apart from those ones,” he says.

Smell is apparently also a good guide. “If you want to know whether a mushroom is edible, smell it and have a guess.” He picks a particularly poisonous specimen called Clitocybe dealbata. “Try,” he says waving it under our noses. We sniff. “What does it smell like?” “It smells like a mushroom,” says one pupil. The others nod. Raoul looks depressed. He changes tack. “I think the best rule is, if you're not sure, don't bother.”

My fellow foragers would tend to agree. “I'm not convinced I'd do this on my own,” says Anna, a writer from London. Rob, her boyfriend, agrees. “I think this course might make me a more adventurous forager in the supermarkets,” he says. “I'll now feel emboldened to choose some of the more exotic mushrooms in Waitrose.”

However Raoul is convinced that foraging is not dangerous if done properly. “Use a book to acquaint yourself with a couple of species, and then only go for these,” he says. “There are plenty of edible mushrooms that are easy to identify.”

A few hours and many more mushrooms later, we return to The Foxhunter to deliver our basket of foraged food to Matt Tebbutt, the chef and owner.

Matt combines our finds with the other food that has come in that morning. Throughout the day local foragers drop into The Foxhunter, bringing what they have found, trapped or shot. The pub bases its menus around whatever appears. “If someone turns up with a big salmon they've just caught, we'll scrap whatever other menu plans we had and go with that,” he explains.

The stress of such ad hoc cooking, he says, is more than outweighed by its interest. “Foraged food is fresh and unusual; it keeps things exciting.” Some of the foods that appear are so unusual that modern cookery books don't deal with them. “I have to turn to the likes of Mrs Beeton or Eliza Acton to find out what to do with some of the stuff,” Matt says. “Then I have to turn somewhere else again to find out what the hell those ladies mean by a quart.”

In the stone-flagged kitchen, the mushrooms are mixed with butter and sprigs of rosemary, then fried for a few moments - wild mushrooms are so delicate, they need little more. Our foraging menu consists of sweet chestnut soup and locally shot pheasant served with the locally gathered samphire and mushrooms.

The finished dish, with its crispy emerald samphire and jewel-bright mushrooms, is carried out with some cere-

mony to the waiting foragers. With such archaic ingredients, the menu is the height of culinary fashion and would be extremely expensive to prepare if one made it using shop-bought ingredients.

But almost all of it has been garnered free from the hedgerows. We tuck in with smugly self-sufficient greed. Yet we all pause nervously before the first mushroom. We check its gills. Not white. One brave soul bites in and chews. He doesn't die. “It's not poisonous.”

Foraging trip and wild food lunch at The Foxhunter, £125 for two people; £35 for each additional person (01873 881101).

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