It's hard to keep up with David and Stephen Flynn, the twins behind the Happy Pear cookbook, and two Greystones cafes of the same name. We meet at lunchtime in their cafe. They have been up since 6am making soup.

Their almost daily photo of the sunrise over the sea in Greystones is on Instagram, they have done some yoga in between filming segments for Ireland AM, and they are excited about testing their new coffee-bean roaster. They record snippets of their day on Snapchat, and their energy is obvious in their YouTube videos. None of it is an act for the cameras. They are effervescent, and their enthusiasm for healthy food is genuine.

“When you’re doing something you love, you just have energy for it,” says David. “Start me at 5am any day and I’ll be flying, but find me at 11pm and I’ll be gone.”

It is lunchtime on a Tuesday and the cafe – which serves only vegetarian food – is busy. There are queues when I arrive and when I leave. All sorts of people line up for lunch or coffee: mothers and their kids, older people, workers on a break. Despite their passion for it, the pair do not want to push vegetarianism on people.

“We’re doing our own thing, and if people are interested they’ll come check it out,” says David. “If they’re not, that’s cool too. It’s not about convincing people, because then there’s an us and a them. It’s just us doing our thing and having a good time. Having a great time, actually. It’s the best game I’ve ever played.”

“People get caught up in the titles. I remember being a righteous vegan for about a year,” says Stephen. “We found initially when we started doing the Happy Heart [their health-education course], we were a little bit righteous about it, and ‘You must do it’, and we realised it creates friction.”

They both eat a vegan diet and have done so for 14 years. They became vegetarian, somewhat spookily, on the same day despite being on opposite sides of the world, as they travelled separately after graduating from their business degrees. They tried multiple diets, from vegetarian and vegan to fasting and raw foods. Today they don’t like to label how they eat.

“I don’t define myself as anything really, because it’s like a religion: saying that you’re a Buddhist and someone else then going, ‘Well, I’m Catholic’ or whatever. I just eat food and mine happens to be vegetables. I’m not part of any club, and it’s not about being more righteous than anyone. I found this works for me,” says David.

Best-selling book

Their cookbook, The Happy Pear: Recipes and Stories from the First Ten Years, contains just vegetarian or vegan recipes. It was Penguin Ireland's first cookbook.

It was a No 1 best-seller for two years in a row, and before Christmas it was announced that it had outsold Jamie Olivier, Nigella Lawson and Donal Skehan, who all had new books last year. "It was totally mad. I enjoyed emailing Jamie, going 'Ha ha, Jamie,' " says Stephen.

Their YouTube channel is affiliated with Jamie Oliver’s channel and network, FoodTube, so they make videos for Oliver’s channel too. It was something that they put off for a while, but it has ultimately been very positive for them.

“It’s been wonderful to work with Jamie and his team and see how they work, and really get to know Jamie himself, and go, ‘Wow, you really do walk your talk’. It’s been really inspirational and fun to work with them,” says Stephen.

In very twin-like fashion, they finish each other’s sentences constantly. The pair are constantly together – they describe going to separate colleges as an “enforced divorce by mam” – and they seem entirely confused when I ask if they ever get sick of seeing one another. “We don’t know any different. We shared a wardrobe until we were 20. ‘First up, best dressed’ was true for most of our life,” says David.

Being twins has been beneficial for business: it has made them feel comfortable taking risks and allowed them to feel constantly supported. “If you watch Hollywood movies, people are always looking for their other half or someone to be connected to, but certainly, in our case, we’ve always felt we’ve had that: someone who’s there for you and understands you to the power of 10. You always were Flynn twins; you weren’t David or Stephen. Who’s David? I don’t know who I am without the other one,” David says.

Other brothers

The Flynn twins have two other brothers: Mark, who’s a DJ in Berlin, and Darragh, the youngest, who runs a sprout and wheatgrass farm and helps run Happy Pear. “Mine and Dave’s skill set was never structure and order and control; it was more about great ideas,” says Stephen. “Darragh’s very good at that stuff, so he helps balance our many weaknesses.”

“We started it as the Happy Pear and, because we were identical twins, in the family we used to get more attention,” says David. “We started the business as two twins, and then he ended up getting dragged into it. We’re quite strong characters and he’s happy. He’s quite gentle and saintly.”

Between the two ventures they felt what they were doing was “very left-of-field” at the time. “When we started, the amount of people from college and Greystones who looked at us with pity, going ‘What the f*** are you two doing?’ ” says Stephen.

“You’re cursing again,” says David. “Health has become cool. People are prioritising health and seeing that what you eat has a huge impact. When we started, we’d a juice bar for five or six years, but after that you couldn’t sustain it. People weren’t prepared to pay €4 for a glass of juice. Now it’s all the rage. It’s really changed massively. Kale is cool. Quinoa is cool.”

"They were cool, though," says Stephen. "They're nearly passé. What's this year's one? We're on to turmeric."

They correct each other constantly. David calls out Stephen for cursing several times, and Stephen cuts off David’s rambling. It’s about the only indication that there is some calculation to the chaos that began with anarchic management in 2006 (“It didn’t f***ing work,” says Stephen) and continued with big ideas.

The pair are savvy businessmen but maintain a clean image. What is their vice? Working too much. “We’ve to find the balance between family life [they have two children each] and our perpetual turned-on-ness for work,” says Stephen. “You’d like to be better at structure.”

“But I like the chaos of it all,” says David.

Their schedule is intense: a series of theatre talks, Happenings, began last week; their Happy Heart course is ongoing; they have a new studio for filming YouTube videos; a second book is in the works; and there could be television show this year. The last two of these projects are geared towards a more international audience and shrouded in secrecy.

When they opened the cafe in 2006, they decided they were starting a “healthy food revolution”. Ten years on, they feel it’s going pretty well. “I think people are ready and are more open to change and eating better and taking responsibility for what they eat, and there’s other stories out there other than the meat and two veg or the old food pyramid,” says David.

THE ULTIMATE CHILLI: SERVES 4

This Happy Pear recipe is great served with brown rice, baked potatoes or toasted wholemeal pitta bread and accompanied by crème fraîche or sour cream.

Ingredients

• 1 red onion
• 4 cloves of garlic
• 1 red and 1 yellow pepper
• ½tsp ground chilli or 1 whole fresh chilli
• 2 courgettes
• 2tbs oil
• 1tsp cumin seed
• 2tsp salt
• 1 x 400g tin of red beans (kidney/aduki)
• 2 x 400g tins of chopped tomatoes
• 100g tomato purée
• 1tsp ground coriander
• 1tsp ground cumin
• ¼tsp smoked paprika
• ¼tsp freshly ground black pepper
• 1tbs honey
• 20g fresh coriander
• Juice of half a lime

Method

Peel and finely chop the onion and garlic. Deseed the peppers, and the fresh chilli if using, and slice them and the courgettes.

Heat the oil in a big pan and fry the onion and garlic on a medium heat for five minutes, stirring regularly to ensure they don’t burn. Add the sliced courgettes and peppers along with the chilli, cumin seeds and salt, and fry for a further five minutes.

Drain the red beans and rinse thoroughly. Add to the pan with the tinned tomatoes, tomato purée, ground coriander, ground cumin, paprika, black pepper and honey.

Turn the heat to high and bring it to the boil, then reduce the heat and simmer for 10 minutes.

Finely chop the fresh coriander and stir through with the lime juice. Taste, and season with more salt and pepper if needed.