Ella Walker meets Henry Firth and Ian Theasby, who have discovered the world of veganism has really opened up since their debut cookbook.

Henry Firth and Ian Theasby are what you'd call sprightly. The Yorkshire-born housemates and business partners are the irrepressibly positive minds behind 'social media sensation' BOSH!

The plant-based recipe platform has had more than 1 billion views to date, and the duo, both 34, are now on their second cookbook, BISH BASH BOSH! "It had to be called BISH BASH BOSH!" says Firth, throwing his arms into the air gleefully.

This one, they explain, is full of all their favourite meals - especially ones nicked from restaurants, takeaways and childhood memories; ones they'd wanted to "veganise" but hadn't managed to squeeze into their debut collection.

It's only been 12 months since the first BOSH! recipe collection was released, but in that short time, the friends have seen a major shift in attitudes towards veganism and the availability of plant-based products.

In the first book there was no seitan, little jackfruit, and "we didn't really do any of these quirky fake meats, we just wanted vegetables", they note. But this time around they've been vegan adventurers. Expect seitan burgers, 'pulled pork' jackfruit and 'tofish' finger sandwiches.

"The landscape has completely changed," says Theasby. "Now you can go into Sainsbury's and buy banana blossom, whereas before you'd walk in and barely find jackfruit, and now jackfruit's a staple."

The general feeling and chat surrounding it has developed too. Firth believes we've got to a place "where it is OK to eat vegan 'chicken nuggets' and to present them at a dinner table to a meat-eater - and not have to have an argument about it".

In fact, when a few years ago they might have come up against quite a bit of griping and hassle from non-vegans, these days, not so much. Partly, Firth reckons, it's "because our stance is quite chill", and even little knocks from family and friends have practically subsided. "The mocking in the last two to three years has kind of stopped," he muses. "More and more people are trying a little bit of vegan food, and it's becoming more and more OK to dabble."

Theasby admits that some people "still don't get vegan food", so part of their plan with BOSH is to make the whole no-animal product lifestyle more alluring, and one way to do that is to go huge on plates that are kaleidoscopic with colour.

"It's good to package it in a nice colourful way," says Theasby.

"Colour is a great way to promote plant-based food," adds Firth. "Less beige, more rainbow."

After all, even though it's more than possible to survive solely on chips as a vegan, Firth is adamant: "You won't thrive."

"It'd be really, really easy to be an unhealthy vegan," agrees Theasby - but that's not their style, hence chapters on nutrition and meal planning, so you can find a healthy balance that suits you.

The potential health benefits of veganism weren't what first drew them to it though. For Theasby, he was on a "crazy" challenge that eliminated meat and booze from his diet, for which Firth "ridiculed him". And then they watched Netflix documentary Cowspiracy on a huge screen - and that was it, for both of them.

"I remember at the end of it, just being [like], 'Woah, oh my god, I've got to go vegan'. I was really annoyed," recalls Firth, who, four years ago, would be found happily munching down on steak or fish and chips. "I was annoyed because I loved what I ate and I didn't want to make the switch," he says, but after Cowspiracy, he realised he couldn't call himself an environmentalist and not go vegan. "Best decision I ever made," he says with a huge grin.

"It's great because you feel so good. Two, three, four days in, there's this lightness of being that stays with you, that helps you persist - as long as you're not just eating pasta and chips."

For Theasby, the main continuing annoyance for him is the effect veganism seems to have on his hair - seriously. "You have to go and get your hair cut more, because it grows faster," he says, jokingly morose. "I used to go once every five weeks, now it's every four!"

Hair troubles aside, confront them with a person who says they don't like vegetables and the duo will crush you with optimism. "They need to come round and have dinner with us!" yells Firth, as Theasby starts explaining how to blend mushrooms down into a creamy sauce for pasta, so you don't even know mushrooms were ever involved.

Firth then starts stabbing his finger at all the different dishes on the cover of the new book, saying: "If you don't like vegetables, that pizza's good for you, that 'pulled pork', lasagne, cheesecake - to be honest there's only one thing on there that even looks like vegetables [their tomato and avocado heavy 'nuevos rancheros' breakfast]."

You can't argue with them. They even tackle Brussels sprouts. "Indeed we do," says Theasby. "And we don't just take them on, we beat them down, haha."

In another 12 months' time, Firth's hope for veganism is that it will "drop the ism" and "become, like, everywhere - something that everyone is down with, whenever they feel like. Some people will do seven days a week, some will do one day a week, but it just becomes normal."

"It's less a hope, more an expectation that that's what will happen," adds Theasby. "All the signs are there."

BISH BASH BOSH! by Henry Firth and Ian Theasby, photography by Lizzie Mayson, is published by HQ, HarperCollins, priced £20. Available now.