It's the first time food has featured so specifically in the annual music programme, which this year celebrates the 200th anniversary of the Norwegian constitution and Orkney's enduring links to that country.
Forselius, from the remote former mining town of Roros, near Trondheim, is renowned for re-establishing the indigenous foods and traditional recipes from his area, and for reviving the artisan food industry. The multi-award-winning chef and hotelier - who owns four restaurants, a deli and a brewery - has appeared on numerous TV shows across the world, and written four books, the latest entitled Foraging. He will come to Orkney for the first time to devise a selection of dishes for the St Magnus Festival audience as they listen to the Trondheim Soloists perform a sell-out programme of music to mark the feast of John the Baptist.
Although he hasn't yet finalised his menus, he's keen to create something that will give audiences the experience of something new - using Scottish produce. "Hopefully I can do something with my food that matches their delight with the music," he says.
He frequently cooks with the malt and hops discards from beer-making, especially in bread using a 16th-century recipe. He will make this bread on Orkney and serve it as the basis for canapes including confit of wild Scottish salmon with confit of free-range egg (baked in rapeseed oil, sea salt and herbs), cauliflower cream and beetroot sauce; Scottish herring with Norwegian sour cream (from unusual soured milk called Tjukkmjolk that has been produced in Roros for centuries, and was the first local product in Norway to get legal protection); creme brulee of eggs, organic fermented milk and cloudberries; and a dessert of wild strawberries with rhubarb and cream.
Although trained in the classic French tradition, Forselius, 40, sources local, organic ingredients and says that 90% of everything he cooks is from within 150 metres of Roros.
"I was working like this before Rene Redzepi made the trend famous," he says. "My restaurants and hotel are not Michelin-starred but the food we serve is high quality, in a small town in the centre of Norway. It's not fine-dining, it's a more common style for the local people, and for the tourists, to give them a taste of my area. I only work with ingredients in my area, which is 800 metres above sea level and special."
There are undoubted parallels with Scotland, where many chefs are tuning in to local indigenous produce for their menus.
"The long daylight hours and low temperatures here mean ingredients grow slowly, giving them a sweeter, more intense, richer flavour. One thing that's important to me is to know where items like carrots have been grown and how they taste," he says.
"If you shut your eyes when you taste my food, you should feel and taste the things that the animals have eaten, find the herbs from the mountains and the minerals and berries. The exact choice of ingredients is mine, but this kind of food has been made here for centuries and it is my mission to continue that tradition."
Forselius, who was born in Sweden and trained at the two-Michelin-starred Grand Hotel, Stockholm, started working like this in 1996, at a time when small food producers were "in a plight" because the big co-operatives were "taking in all the milk and meat from the country". With funding from the Norwegian government, he helped farmers and supported small-scale artisan producers, encouraging more inward investment. In the last year alone, more than 100 small producers have sprung up, making items with milk curd, reindeer meat, soft fruit, herbs, potatoes and so on. This is what informs his cooking. He insists that it is no longer necessary for chefs to be trained in the classical French tradition as it was 20 years ago; now, he says, "you can start your career in the new school Scandinavian cuisine".
"I am proud of what I have done," he says. "I have my own special herd of cows for the restaurants and shop. Years ago, the local milk co-operative ran out of money so it was close to being shut down. Only four people worked there. We bought it with funding from the government and now it's the most successful in the country making butter, cheese, and traditional fermented milk made from grass enzymes to a recipe from the 1700s. It's a huge success."
However, funding for farmers may be cut under the newly-elected conservative government, and he is keen to work with them to find a way forward. "It will be very difficult for me if the government cuts funding. I need all my small farmers and their wonderful products; I buy from them directly at a good price. The number of farms is already shrinking. We need to be able to continue to source exclusive ingredients. My area is high in the mountains, producing high quality butter, special things exclusive to the area like small almond potatoes, cloudberries, wild river salmon, free-range lamb and reindeer meat, from 1500 metres above sea level.
"Such ancient local ingredients are a big part of our cultural identity and it would be disastrous if we were to lose them. Cuts will also affect the tourist industry, because if you don't have farms with sheep and cows cultivating the land, it becomes neglected. The landscape is important to the tourist industry. If you only see forest as you travel through, it's not so interesting and people won't be so inspired as they are now."
He is a firm believer in the power of food, like music, to move and inspire, and its links with cultural identity. He is looking forward to seeing Orkney and all it has to offer in terms of local produce. Though he won't get to the mainland this time, he is aware of the high reputation of Scottish produce and says: "In terms of food, Scotland and Norway have many things in common."
The 2014 St Magnus Festival, June 20-26.