The chef and his collaborator Belfrage chat to Prudence Wade about their new vegetarian cookbook, Flavour.

When talking about food, the word 'fusion' can strike fear into a diner's heart. More often than not, it suggests mismatched dishes chucked together with relatively little thought or consideration.

However, Yotam Ottolenghi and Ixta Belfrage are here to change your mind - and respect is at the core of everything they do. Ottolenghi is a giant in the food world - known for his cumin-heavy cookbooks, colourful London delis and restaurants, and his love of pomegranate seeds - and for his latest book he's collaborated with Ixta Belfrage, who worked in his test kitchen for four years.

The result is Flavour, a collection of exciting new dishes paying tribute to a range of cultures - and incidentally, it's all vegetarian. Like Ottolenghi's previous veggie cookbooks - including Plenty and Plenty More - this is a real celebration of vegetables, not sad beans on a plate.

Ottolenghi says the pair's approach to writing the book was "pretty similar", but they brought "very different backgrounds" to the table. "My background is deeply rooted in the Middle East," explains Ottolenghi, who was born in Jerusalem. "I've lived here [England] for more than 20 years and gone through my own trajectory. Ixta has less experience writing books, but tonnes of experiences from being all over the world, and a really interesting background that includes Mexico, Brazil, Italy and France. And so all these stories came together."

Belfrage explains her "mother is Brazilian and grew up in Cuba via Mexico, so there's south and Latin American in my heritage; in my upbringing; the kind of food I ate, and where I travelled when I was growing up." She moved to Italy when she was two-and-a-half, and says "that's really what feels like home to me, and the food feels like home to me."

With varied backgrounds capitalising on different ingredients and flavours, you might wonder how the book could come together so seamlessly. However, a similar approach to food ties the duo together, with Ottolenghi explaining: "We both love big flavours and big gestures. Intensity is definitely something we have in common, but the details are quite different" - and the recipes reflect this.

Whether it's swede gnocchi with miso butter, za'atar cacio e pepe or caponata with silken tofu, the recipes marry together global flavours. For Ottolenghi, "all these cultures" are united by one thing: "The human palate. We're attracted to certain flavours, so if you substitute anchovies with miso - these two things are from quite different cultures, but they both involve the same level of saltiness, umami, fermentation - things that are really cross-cultural. So it doesn't take a huge leap of faith to substitute one thing that may have been in a dish from one culture, with another from a different culture."

The main issue is "being sensitive when you do that," he explains, "so it actually does work. You don't mix things just for the sake of it, but you mix it up when it makes sense and is delicious." Belfrage agrees, and says "one does have to definitely acknowledge where it comes from."

Something else uniting Belfrage and Ottolenghi is their roundabout way of getting into the food industry. Ottolenghi completed a master's degree in comparative literature and was considering pursuing a doctorate before changing direction to study at the Cordon Bleu. Belfrage never formally trained as a chef and says she did "lots of random things" before setting up her own catering company and market stall selling tacos.

Both chefs now see this as an asset. As she didn't have professional training, Belfrage says: "I definitely don't go about cooking thinking there is a certain set of rules that need to be followed, or ideas that might be taught at cooking school. I don't think there are any rules when it comes to combinations about flavour."

"I also don't have very much experience in restaurants," she adds. "I just picked things up along the way, and that's informed the way I cook."

Anyone who's read an Ottolenghi cookbook, or has seen the chef speak, will know he has a beautiful grasp of words and way of talking about food - no mean feat. "I think it's all a big mixture; the cooking, the talking about food, and the ideas that come around it," he says thoughtfully. "I guess it reflects your personality, and both Ixta and I have had very varied experiences professionally.

"Food is never in isolation - it's about how you cook, how you present it, what you say to the world, what you say to yourself."

Ottolenghi FLAVOUR by Yotam Ottolenghi and Ixta Belfrage, photography by Jonathan Lovekin, is published by Ebury Press, priced £27. Available now