A little more delicious strychnine and butter sauce for your fish, vicar? Or a slice of that scrumptious cake, so appropriately named Delicious Death?

A unique cookery demonstration is to be held to celebrate the 125th anniversary of the birth of Agatha Christie, the Queen of Crime. It will be in Christie’s own Devon kitchen, and guests are advised to treat samples with extreme caution.

The French writer Anne Martinetti will be recreating recipes from Christie’s books, singling out those particularly suitable for concealing poison as an extra ingredient. As any devotee of Miss Marple or Hercule Poirot knows, the great detectives only have to show up for a morning coffee, light luncheon or afternoon tea party for one of the guests to topple over the table clutching their throat and turning blue.

Martinetti will be speaking and cooking at Christie’s beloved holiday house, Greenway – the home she called “the most beautiful place in the world” – now in the care of the National Trust.The event is part of the Agatha Christie festival this September, held in and around Torquay where she was born on 15 September 1890. Food, not always lethal, figured heavily in Christie’s books and in her real life. Festival director Anna Farthing recalled that Christie often noted after social engagements that the company had been trying but “the eating good”. An archive photograph shows Christie at work in the rather grim kitchen of the beautiful Georgian house on the river Dart, where her grandson Matthew still remembers delicious meals cooked by Granny.

Martinetti has carved out a unique niche in the overcrowded coffee-table cookery books realm: criminal food. Her books, with diabolically punning titles, include Alimentaire Mon Cher Watson!, of Sherlock Holmes recipes, and her Agatha Christie volume, Cremes et Chatiments, or Creams and Punishments.

“I’m very excited and impressed to cook at the same place where Agatha Christie was, especially when I see the photo of her with her apron,” Martinetti said. “It will be a great experience for me, and I hope that the soul (or maybe the ghost) of Dame Agatha will smell the perfumes from the recipes and enjoy.

“I think I will share the cake called Delicious Death cooked in the novel A Murder is Announced – it’s a fabulous chocolate cake. Maybe I will also prepare fish butter, the weapon in Sad Cypress, and let people guess if I have added strychnine.”

Belinda Smith, of the National Trust, said it would be a unique event. “We know how much Agatha and her family enjoyed the time spent at their holiday home, having meals together at the very table Anne and her lunch guests will also use.”

Poison was a favourite weapon in Christie’s books, though Martinetti said: “If I would kill someone I think I would use a violent weapon – like in Shakespeare plays, you know?” Christie knew the subject well, having worked dispensing medicines as a volunteer in both world wars. Poison will also feature in several other events in the festival, including a guided tour of the poisonous plants in the garden of Torre Abbey and a lecture by Kathryn Harkup, author of the forthcoming A is for Arsenic, a book-by-book analysis of poisons, from arsenic to veronal, in Christie’s work.

Farthing said the organisers had worried that people might think the festival was offering a how-to manual. “But, I cannot stress too highly, with modern forensic techniques you absolutely definitely will now be caught and convicted and spend the rest of your life in prison.”

Nonetheless, Martinetti and Harkup agree that good quality dark chocolate is ideal for concealing the bitter taste of poison. The Delicious Death cake made its appearance in A Murder is Announced, touted as Christie’s 50th book, published in 1950 and greeted by the Guardian as “murder run to earth in a brilliantly conducted parlour game”. In the recipe recreated by Martinetti, the sumptuous ingredients – including 250g of dark chocolate, 12 eggs, and a lavish glug of Cointreau – would after years of postwar rationing have stunned 1950s readers as much as her final ingredient: “strychnine (optionnel)”.

Despite recent million-sellers including JK Rowling’s Harry Potter and the apparently innumerable Shades of Grey of EL James, Christie remains the world’s bestselling author, according to David Brawn of her publisher HarperCollins.

“The figure often quoted, which we believe is about right, is 2bn copies, a billion in English and a billion in other world languages, still selling at the rate of 4m to 5m copies a year. That 2bn figure was arrived at by Unesco about 10 years ago so it will have risen since then – but really, after the first billion or so, who’s counting?”

The 125th anniversary International Agatha Christie festival will be held in Torquay, Devon, from 11-20 September.