What Sam Sheffield-Dunstan doesn't know about picnics isn't, frankly, worth knowing. But during July and August, you'll rarely catch her relaxing in a deck chair, enjoying delicious food and wine.

"I'm madly busy," she says, expertly halving a freshly cooked lobster. "We've been sending out picnics for weeks now as fast as we possibly can. It's been a great summer so far."

Mother to 18-month-old Amelie, Sam runs a company called Gourmet Picnics from her home in Porthleven, West Cornwall. She has kindly agreed to share some inspiring ideas for portable, but mouth-watering, food.

"The key to a great picnic is that it should be easy to cook, carry around and eat on a rug somewhere. But that doesn't mean you should settle for boring sandwiches," she says.

Sam ships the finest produce from her part of Cornwall – including caught-that-morning crab, lobster and local cheeses and even Cornish bottled water – all over the country. Thanks to her head chef Bruno Helebrandt, the food arrives completely ready to be laid out on a rug somewhere sunny, and then enjoyed.

"I got the idea when I was living in Australia several years ago," Sam explains. "I went on a trip into the countryside and a catering company provided a hamper. I was expecting filled rolls and orange squash – maybe some crisps if I was lucky. To my surprise, I opened it up to find salmon en croute and a bottle of Hunter Valley wine. It was light years away from the sort of thing you'd be offered in the UK. It lodged in my mind as an idea for a business – one day."

And that day has certainly arrived, with Gourmet Picnics now a regular feature of the al-fresco eating scene at the opera in Glyndebourne, open-air theatre in London's Regent's Park and even concerts at Scotland's Leith Castle. "Our latest challenge is a picnic next week for 150 guests at a wedding party in Kent," says Sam. "It's a bit daunting just in terms of the quantities, but we're looking forward to it."

And her picnics also often feature in the very earliest stages of wedding planning. "We get a lot of men who order from us when they are planning to propose. I always insist they let me know if she says yes. So far we have a 100 per cent success rate."

One can certainly see why one of Sam's picnics might create the right sort of romantic ambience – and be perfect for a gent who isn't up to cooking gourmet-style himself. It arrives chilled with everything included, from the freshly baked bread to the best champagne, and even biodegradable wine glasses, plates and cutlery. It's all delicious too. Everything from the chilli crab cakes to rocket and pancetta salad is prepared by Sam and Bruno first thing in the morning, then sent by courier to arrive within a day.

"We have close links with one of the Porthleven Harbour fishermen, known to all and sundry as Budgie, who catches our crab and lobster for us," says Sam. "I can actually see his boat from my window and watch the seafood being landed. Then we cook it that morning and off it goes – unbelievably fresh."

All bread and the antipasti of chargrilled artichokes and roasted red peppers are given a special flavour by being cooked alongside glowing logs in Sam's wood-fired oven.

"It's been a real adventure getting this business up and running, but so worth it," she says. And yet she so easily could not have ended up in Cornwall at all, were it not for a chance meeting on the Paddington to Penzance train in 2005.

"I was coming down to visit my parents, who have retired in Cornwall. I got talking to what seemed like a very nice guy. By the time the train crossed the River Tamar, we'd swapped contact details and agreed to meet up."

Mark, a builder, is says Sam, "as Cornish as can be" and is now her husband. "We got chatting, and before I knew it my life had changed totally. Now I'm so settled here and I absolutely love Porthleven.

"I knew the area well as I'd studied art at Falmouth when I was younger. But I worried that if I moved to Cornwall I might miss the pace of London life. So it made sense to start my own business."

The memory of the delicious Australian lunch came back to her and so she launched Gourmet Picnics. It has proved so successful that last Christmas she also took on an old smokehouse on the quay at Porthleven and has transformed it into a cafe-restaurant called Amelies.

All in all, it's been a busy few years. "For now, though, I'm really happy and so proud of what we've achieved here," she says. "I take the view that all our picnic food must be from producers as close to us as possible and the best-of-the-best in terms of quality. Luckily that's pretty easy to achieve in this part of the world."

Perhaps it's not so surprising, then, that food-lovers from as far afield as Scotland clamour for Cornish picnics these days. To prepare your own version this summer, why not try some of Sam and Bruno's recipes?