A, B, seafood - Martin Wishart

Martin Wishart recommends the hands-on approach to teaching youngsters about healthy eating

There is one moment more than any other that grabs the attention of the dozen children in the kitchen of Martin Wishart's Cook School and holds it tight as a vice. The celebrated chef is demonstrating how to prepare fish and shellfish and has handed one boy a live lobster.

He has eyes the size of saucers and a fixed, nervous grin as he holds the crustacean by its mottled black shell at arm's length while his classmates quickly step away from the lad with the lethal foodstuff.

Its powerful front claws could take a finger off, but they've been rendered harmless by blue tape. Yet still the boy holds his arm up straight, keeping the lobster as far from his body as possible. And no wonder: the crustacean is still restless and when a pen comes into range of its small back claws, the lobster grips it as if its life depends on it. It doesn't – the only remaining certainty in its life is that it will end up on a table in Wishart's eponymous Michelin-starred restaurant in Leith before the night is out.

As he explains this to the assembled children, we all know the next question. "So how do you kill the lobster?" asks the boy, speaking for all 12 of them. There's a moment's silence in which I mentally beg Wishart not to say that he's going to boil the little sucker alive; most children love gore but there will always be one who is kept awake for months by visions of lobsters perishing in a bubbling hell of boiling water.

Their necks crane forward and they stare at the chef as he briefly considers the question, but Wishart has been dispatching lobsters and crabs since he was a small child unloading creels on holiday in Shetland and doesn't stand on ceremony. He simply leans forward, grabs the lobster, slaps it on to the work surface and whips out a long chef's knife. "You stick the knife here," he says, positioning its sharp point in the slit that runs right behind the two beady little eyes which are now flickering wildly, "and you push down as hard as you can, pushing the point into its brain. It kills it instantly."

There's a general impressed murmur. Not one of them seems remotely bothered by the idea of fishy death in the morning.

I'm in Leith to witness Wishart's attempt to plant the culinary seed in the minds of a group of impressionable 12-year-olds from Flora Stevenson Primary School in the Edinburgh suburb of Comely Bank. He's chosen fertile ground: with every pupil in the 30-strong class begging to attend, there was a ballot that produced 12 lucky winners.

A father himself, Wishart's experience with four-year-old daughter Clara has given him a valuable insight into keeping a child interested in the kitchen. It's also proved to him that early exposure to a range of tastes develops a child's palate very quickly: Clara's favourite nibbles include capers, olives and gherkins. Not only that, but Wishart has also been helping nurture his nephew Rob's burgeoning interest in cookery. The 12-year-old now makes a good proportion of the family's meals and several varieties of his own bread. It's difficult not to think of my own 11-year-old at this stage: he can barely make toast.

Wishart has discovered that children react well to his deadpan delivery, and he's not one to let an opportunity to spread the good food gospel go a-begging. He developed an early interest in food when a friend's father managed the old Crest Hotel on Queensferry Road. He was allowed to hang around the kitchen, where he was fascinated to the point of fixation by the live lobsters and crabs.

The result is a messianic enthusiasm for teaching children how to enjoy what Jamie Oliver would call top tucker, a passion that has translated itself into an evangelical "give me the boy and I'll show you the Michelin-starred chef of the future" mission. "The idea is to inspire kids so when they go home they try new ingredients and make their parents think about what they're eating," says Wishart. "I'm trying to spark an interest in food because at the age of 12 they've still got great imaginations and a willingness to try new things."

Wishart first dabbled with inviting children into his kitchen over two years ago, and this class is just the latest of several, with more to come: this summer he is running day-long courses for youngsters who want to learn the basics about food. Not that this gaggle of schoolchildren mind being guinea pigs. Even leaving aside their understandable glee at spending a morning missing maths and English, their eagerness to learn is unmistakable.

The big, airy room is divided into three 'stations', each with its own chef who instructs a team of four children. The recipes focus on how to make simple staples and include hamburgers, quiche, bolognese sauce, bread and sausages. Wishart's priority is to produce dishes that can be cooked at home because he believes it's there, rather than in the school canteen, that a genuine appreciation of healthy food can be most effectively inculcated.

The first of the three stations is manned by Wishart, who is teaching his four eager charges how to make tomato ketchup. For the avoidance of doubt, this bears no relation to the stuff that supermarkets sell. For a start, it's stuffed with spices and the first part of the lesson is to get the children to identify the contents of five small, white bowls. Incredibly, Varshini Vijayakunar knows them all and points to each without hesitation: there's star anise, cloves, cinnamon, fennel and coriander seeds, all in their natural state. "My mum uses spices a lot," she says, "and I like to help her cook." Cook what, I ask? "Oh, I like everything my mum cooks, but roast chicken is my favourite."

After the spices have been identified, piled into a muslin bag and put into the pot, in come the tomatoes. They're to look for ones that are past their best, that are red, soft and squidgy. Wishart explains how to blanch the tomatoes by plunging them into boiling water and then running them under cold water so that their skins drop off. Then he shows them how to remove the acidic pips by scooping them out with his fingers. The chance to get their hands dirty goes down a storm.

Anna Hale is also helping make the tomato ketchup, chucking in the gastric (equal parts sugar and white wine vinegar – a concoction that balances out the sweet and sour flavours of the sauce), caster sugar, vinegar, salt, bread, slices of ginger and water, then watching it simmer. Just before it's liquidised, Wishart scoops out a teaspoon of the crimson liquid and gives Hale a taste. "Wow, that's just got so much flavour in it!" she says, clearly surprised.

At the station next door, Bruce Rennie, the head tutor and, until earlier in the year, the most senior chef at Wishart's restaurant, is teaching the children how to make pasta from scratch. He has an easy-going, cheery manner and, as a father himself, relates easily to the youngsters.

He shows them how to make the pasta mix, rolling and kneading it like a born Neapolitan. He makes it gradually thinner until it is almost translucent, then runs it carefully through the pasta machine. Within minutes he's made spaghetti, tagliatelle and then he produces exquisite little ravioli parcels that wouldn't look out of place in Wishart's restaurant.

The children have enjoyed pummelling the pasta mix, their little white chefs' hats quivering as they crank up the physical effort. They listen as Rennie tells them what they could serve with the pasta. When he starts talking about truffle oil, one of the girls notices some bottles of the oil in a glass cabinet: they're little bigger than perfume bottles but they cost £25 a pop. She can scarcely believe it, especially when Rennie opens one and she takes a whiff. "Ohmygod, it smells like old cauliflower," she squawks.

Rennie explains about truffles, how the little balls of fungi grow under trees in France and Italy, and truffle-hunters use pigs and Labradors to find them, and that white truffles sell for £2,300 a kilo, more than the price of gold. This last item leaves them slack-jawed. Finally Stuart Meader pipes up: "But that's more than every PlayStation game ever made," he says. Rennie just smiles.

Across on the other side of the room, pastry chef Ricky Preston looks as though he's icing a cake as he puts little dabs of pastry on to a baking tray. "See, you push, push, push," he tells his four charges. He's teaching Tom Bagshaw, Umar Majid, Daniel McIvor and Ryan Langmuir how to make profiteroles. It's the best job and although all 12 children will visit all three stations, the lads have nabbed the best gig first.

As soon as the choux pastry balls are ready to go into the oven, where they will expand to the size of golf balls in a matter of minutes, Preston turns his back to open the oven door. The boys waste no time in using their fingers to scoop dollops of the light choux paste into their mouths before pilfering some of the deliciously cocoa-rich plain chocolate buttons that will be melted to make the chocolate sauce. It seems a good idea so I do the same.

Young Ryan Langmuir is a trainee gastronome and would-be epicurean who has already decided he wants to be a chef. "I like helping my mum making omelettes, lasagne and spaghetti bolognese," he says. "I like cooking and I want to be a chef. I know it's hot in the kitchen and tiring being on your feet all day, but I don't care about that; it'd all be worth it to be a chef."

As the children finish at the last station, they all munch manically on the profiteroles. They disappear in seconds, with class teacher Kirsten Shannon and classroom assistant Susan Bowden performing as admirably as their charges in the speed-eating stakes. Several of the youngsters have a profiterole in each cheek: they look like super-sized hamsters.

As they gather around, Wishart shows them a tray of vegetables containing everything from beetroot to Jerusalem artichokes. The children, to be frank, look fairly nonplussed. They perk up when he takes them to a worktop strewn with seafood. This is where they meet the lobster, but that is by no means the only fishy star turn. "Who can tell me what this is?" asks Wishart, holding up a haddock. "Er, is it a fish?" comes the reply. Even the great man is temporarily lost for words.

There are flat fish, white fish and even a monkfish, arguably the ugliest critter in the ocean, from which the children recoil. Wishart wants to show them how to take raw ingredients to the point where they can eat them, so first he picks up a mackerel before gutting and skinning it, then putting strips into the frying pan. Ryan is allowed to fry the fish as his classmates look on, and when Wishart is satisfied it is cooked, it is cut into small pieces and offered to the children. They descend like locusts.

Next it is the scallops. There are "oohs" and "aahs" as Wishart splits open the shells and scoops out the orangey skirt before sizzling the scallop in the pan and squeezing lemon over the top. This time it isn't just the youngsters who make short work of the cooked scallops. Susan Bowden has never tried them and, after much procrastination, finally puts a piece in her mouth. "That's lovely," she says. "Why have I waited all my life to try that?" This is manna from heaven for Wishart. "Because you never got the chance to come somewhere like this when you were young," he quips.

Martin Wishart's Cook School (0131 555 6655, www.cookschool.co.uk) will be running one-day courses for children aged 11-15 on July 9, 23, 30 and August 5, at a cost of £25.

Recipes

Choux paste

220ml milk; 85g unsalted butter, diced; 105g sieved flour; 3 eggs; pinch of salt

Put the milk, butter and salt in a pan and bring to the boil to melt the butter. Add the flour and cook until the mix takes on a sheen. Place the paste in a food mixer and beat until cooled to body temperature.

Beat the eggs in one at a time until fully incorporated. Preheat the oven to 180¼C. Pipe paste balls the size of an adult thumbnail into a silicon tray and cook for 12-15 minutes until doubled in size and gold in colour.

Fresh pasta (makes 500g)

450g plain or '00' pasta flour; 1 tbsp olive oil; 3 tbsp cold water; 3 egg yolks; 1 pinch of salt; 2 whole eggs

Crack the whole eggs into a bowl with the egg yolks and beat together with a whisk. Set aside.

Mix the flour and salt in an electric mixer on a very low speed. Slowly add the eggs and beat to smooth dough.

Add the water and olive oil, then beat on a slightly higher speed until the dough becomes smooth and even, about two or three minutes.

Divide into four even pieces, cover in clingfilm and leave to rest in the fridge for at least an hour.

Tomato ketchup

6 peeled plum tomatoes; 3 slices fresh peeled ginger; 2 tbsp gastric (equal parts sugar and white wine vinegar); 2 tbsp tomato purée; 2 slices white bread, crusts removed; 12g caster sugar; 1/2 tsp celery salt; 100ml water

Cut the tomatoes in half and squeeze out the seeds. Place the tomatoes in a pan with the other ingredients, bring to the boil and simmer for ten to 15 minutes so that the liquid reduces.

Place in a liquidiser and blend until smooth then pass through a fine sieve with a ladle. Leave to cool then place in a container or bottle and store in the fridge.

Note: the ketchup must be used within three days.