If ever proof were needed that appearances can be deceptive, then Shirley Spear is it. Her easy manner and infectious giggle are the attributes of everyone's perfect granny and sure enough, when we meet in an Edinburgh cafe she orders a shortbread biscuit with her coffee and proceeds to share it with me while happily admitting that she can talk for Scotland.

Spear, who joins the Sunday Herald today as the newspaper's resident chef supplying readers with recipes every week, is a woman you can say has definitely got the gift of the common touch.

However, behind the mild-mannered façade is a backbone of Sabatier-strength steel. How could it be otherwise for the Peebles-born public relations executive who turned her back on a career in London to buy, with her driving instructor husband Eddie, a former croft house in remotest Skye and turn it into a world-famous restaurant – all the while bringing up two young children?

That was 30 years ago, when Scottish food was the butt of many a joke. At the Three Chimneys the self-taught Spear helped turn that around by becoming an early champion of local seasonal produce and scouring traditional Scots recipe books to produce such dishes as baked halibut, crab tart, and lamb with pearl barley risotto. The hard work paid off with back-to-back bookings and recognition as one of the world’s top 50 restaurants.

Last year, semi-retired in North Berwick, she had to start all over again. Just months after gaining the Three Chimneys its first Michelin star, chef-director Michael Smith announced his departure, triggering a mass exodus of staff. Spear spent the summer of 2015 frantically curating a comprehensive recruitment drive, mostly using social media. A new team of 30, lead by head chef Scott Davies, is now in place.

And along side all of that, she has also been agitating for the reinstatement of Skye airport.

At the same time, at the age of 62 and a grandmother twice over, she was appointed chair of the new Scottish Food Commission (SFC) whose three-year remit is to advise Richard Lochhead, cabinet minister for rural affairs, food and the environment, on how to turn Scotland into a Good Food Nation by 2025. Its first interim report has just been published.

The experience has been “more rewarding than anything I’ve ever done” though she concedes that changing the food culture to address the nation’s diet and diet-related health problems is akin to “trying to turn around a tanker at sea”.

It has involved attending and speaking at events all over the country, learning about what she describes as the “amazing grassroots work that’s already happening throughout Scotland and where I’ve been welcomed with open arms”.

She says: “So much good stuff is going on it has made me realise the Scottish Food Commission has to become the hub for all that activity. Instead of us feeding out to the nation, the nation has to feed into us so everyone can share best practice.”

She would like to see a nationwide “Building A Good Food Nation” marketing campaign – a Scottish version of the “I’m Backing Britain” campaign of the 1960s - using social media to get the message across.

The report has been criticised by some for not having much content, being insufficiently influential to generate change, and generally being a waste of money – even though all 15 SFC members are unpaid.

"I could say I am hurt by such comments, but that sounds a bit girly,” she says. “In fact, I get very angry and frustrated by them, because these people should know that this is just the start of a massive movement for change that relies on everybody getting on board.

“We now have a plan of action that we can progress. Maybe my critics feel they should have been given the job I have, because they're intellectuals and I'm just a chef who's thinking about what to give the grandchildren for their tea.”

Does she feel there are factions of the Scottish chattering classes who for political reasons will never agree with anything initiated by the SNP government? She hesitates. "I'm not a political animal but the way I see it is that we’ve got a government and even if we don't always agree with it, if you want things to improve you have to engage with it and get involved.”

The SFC is non-statutory. Is she optimistic it can effect change? “It may not have power as such but it has influence. Everyone, from council leaders to managing directors to chief executives, has to pull together. Otherwise it will be the downfall of Scotland.

“Some of the events I've attended over the last year have been funded by different government departments like Health, Education, Social Justice, farming and fishing, and food and drink. It's easy to get the impression that it's quite fragmented, but I'm assured the departments do work very closely together and share information on a regular basis, and that's given me a bit of a lift.”

She recently attended the foodservice industry’s Healthy Living awards and was bowled over by the number or "ordinary middle aged" women picking up gongs for the work they do in, for example, feeding mentally disabled children in an Elgin care home, or students in the canteen of the West of Scotland College in Clydebank. "These women are dinner ladies and they are the salt of the earth, the stalwarts of the nation," she says. “It's older women who know how to cook and to shop for food economically, and they who can teach younger generations how to do it.”

In her Sunday Herald columns she wants to get back to her own – and Scotland’s - culinary roots by championing traditional recipes using local produce for home-cooked family meals. “I want to get across the message that cooking is fun and doesn’t have to be of celebrity-chef standard,” she says. “If I can do it, anybody can.”