Shabbat is the one night of the week when Olivia Wollenberg might feel hard done by. Two years ago, she was advised by a nutritionist to give up wheat, dairy and refined sugar.

"The thing I really miss is challah," says Wollenberg wistfully. "My favourite part of the week was going to buy challah for my family. I'd buy one just for me."

She had suffered from stomach pains for years. "When I was 10 my parents took me to see various doctors. They couldn't find any intolerances or allergies, but at 16 I had glandular fever which seemed to trigger even worse problems.

"I'd ignored it, as I loved food and thought life too short to cut out huge food groups; but it got to the point where I'd be curled up in a ball after dinner. I'd laugh about it but eventually it was no laughing matter."

Wollenberg was given a huge list of foods to take off her plate: "I did an eight-week elimination diet and during that time the food I could eat was so limited - it was terrible. My whole life was about food and cutting out so many different foods made me so low."

The resulting hole in her diet planted the germ of an idea to create indulgent treats, free from dairy, wheat and refined sugar. She set about figuring out ways to make treats after reading various internet blogs about natural ingredients and attending a course run by now well-known healthy food advocate, Ella Woodward (Deliciously Ella) and now counts her as a friend.

One Friday night, she tested one of her new recipes - a crumble free from gluten, dairy and refined sugar - on her family. "They thought it was the best they'd eaten and made me think there could be a business idea there," she recalls.

"A friend recommended I apply for the eight-week business course at UCL."

The former Channing School pupil had got her first degree from UCL and been on a path to academia - with a first degree in psychology, and two Masters degrees (in cognitive neuroscience and paediatric neuropsychology) and a PhD in the pipeline.

She secured a place on the course, but her initial business proposal did not go well: "I pitched my idea for treats that were made with ingredients that were good for you to the course leader, and he said it sounded revolting," she laughs.

She went home, made a crumble and brought it for her tutor to taste. In front of the entire course. "He warned me it might be even more mortifying, but thank goodness, he said it was delicious."

Wollenberg won the mid-term and end-of-term pitch prizes, which amassed her £12,000 to invest in her fledgling business. "It gave me confidence that someone believed in what I was doing." She then went for it, making and delivering hundreds of crumbles, to every magazine, newspaper and food buyer she could find. "My mother and I were making crumbles until midnight."

She adds: "I started experimenting with maple syrup and coconut sugar. I finalised four flavours - berry, banana, apple and rhubarb - and added superfood powders into the toppings: cacao in the banana and vanilla and goji in the berry one."

She says she chose crumble as a familiar and nostalgically British food. By mid-October, her crumbles were stocked by Selfridges, Planet Organic and Daylesford, but she and a team of helpers were still cooking them from her family home. She tried to outsource production, but found the logistics of combining gluten-free with fresh fruit impossible to combine under one roof.

So in March 2015, despite the success of the crumbles, she was to move on to developing a different product under the brand name of Livia's Kitchen. After 20 factory trials, "I am a complete perfectionist and didn't want to disappoint anyone," she developed her raw millionaire bites.

"I test my recipes on people who eat 'normally' and not those on restricted diets as I want to produce food that is healthier but which people who eat sugar also would choose. It took eight months to get it right, and we only launched in mid-February this year."

This month, she published a cookery book of sweet, but free-from treats.

"I pitched the idea to my publisher with just 10 recipes, but when they took it, I had 11 weeks to come up with 100 recipes! I was also trying to produce crumbles for the stores at the same time. It was a fun challenge, but even for me, eating just sweet foods was a bit much. I really immersed myself in it and wanted to understand the textures of what I was recipe testing, so needed to taste recipe throughout the process. On some days I'd have eaten quarter of a chocolate cake by 11.30 in the morning!"

She admits that her recipes can be indulgent and you would not eat them in large quantities, but explains that as they are made with nutritious ingredients, they should leave you feeling better than treats packed with refined sugar and flour.

"I have tried to make the recipes in the book accessible. If you have maple syrup, oats and coconut oil you could make something - they're my staples." She also explains that you can swap ingredients, so that you can use regular milk instead of non-dairy replacements if you prefer. "Whatever you enjoy - it's about what makes you feel good."

Now a picture of shining health, it's working for her.

Visit Olivia's website, Livia's Kitchen

Recipes from Livia's Kitchen, Ebury Press, £20, and available from Amazon