Chef Phil Howard on his new restaurant Elystan Street

Phil Howard is back in the kitchen. His new restaurant, Elystan Street in London, which he has launched with business partner Rebecca Mascarenhas, is his first project after selling the Square. He talks to Andy Lynes about getting his appetite back

It's early September and the imminent opening of Elystan Street, Phil Howard's first project since the sale of the Square to the Marlon Abela Restaurant Corporation in March this year, appears to be giving people the jitters.

When I arrive for my interview with Howard, the Chelsea restaurant is a building site and there has been no opportunity for the chef to trial his newly recruited brigade of 19 (only 25-year-old head chef Toby Burrowes has survived from the Square). I find him in the roomy basement kitchen, struggling to light the range that still bears the name of Tom Aikens, the restaurant's previous occupant. "Where's the fucking blowtorch?" asks Howard of no one in particular, and suggests I wait for him upstairs. I beat a hasty retreat.

"It's all getting a little bit frisky," he admits, when we sit down in what will be the private dining room while the building work continues unabated around us. But once we begin to talk, any signs of anxiety fade, and Howard relaxes into the hour-long interview, giving it his full and undivided attention.

Elystan Street is the 50-year-old chef's third project with restaurateur Rebecca Mascarenhas. The pair already run Sonny's Kitchen in Barnes, south west London (where they are near neighbours) and the Michelin-starred Kitchen W8 in Kensington.

But this is the first where Howard will cook on a regular basis, marking a step change in their business partnership. It's also a watershed in Howard's business relationship with Nigel Platts-Martin, his partner in the Square for a quarter of a century.

"Nigel doesn't have the appetite or desire to open another restaurant, but I'm still a business partner with him and I'm still on fantastic terms with him," says Howard. "I'm still a partner in the Ledbury, but I have no involvement in the day-to-day running. I still speak to Brett [Graham, head chef at the Ledbury] a lot, but he's very much his own man. Nigel plays a very active role there and, thankfully, I just enjoy it from afar."

The end of the Howard/Platts-Martin era of the Square came suddenly, with a seamless handover to the Marlon Abela group, which included all existing staff, happening days after the announcement in the press.

"Once Nigel and I decided that was what we wanted, it all happened quite quickly. We had to keep the Square running to the day we handed it over, so there needed to be a certain amount of confidentiality about it. Inevitably, in the end, it seemed like a clinical execution. It was a dramatic moment. I thought at some point we'd all sail over the finish line and pop Champagne corks but, of course, that's not quite how it happened," says Howard.

Following the Square's sale, there was speculation from Howard's peers that he would disappear to his £1m chalet in Montalbert in the French Alps (Howard and his family are all keen skiers) and open a restaurant in the mountains.

But plans to hire a chef for Elystan Street were quickly set aside, with Howard saying that he will give "110%" to the restaurant. "I want to be central to this place's success. know through all the learning at the Square that it's about excellent recruitment, delegation, communication and empowering other people to execute your vision while being very much around. I'm hoping that in a relatively short period of time we'll nail it and then, on an ongoing basis, I intend to be here for 40 weeks a year. That's a massive commitment."

Initial reports are that Howard and his team have indeed nailed it. London Evening Standard critic Fay Maschler was among Elystan Street's first customers, dining during the reducedprice preview period and the first week of full trading. In her four out of five star review, printed just nine days after the restaurant officially opened, she described a starter of smoked mackerel velouté with Porthilly oysters, leek hearts and eel toast as a "secular transubstantiation of humble ingredients into something ethereal".

Another dish, roast grouse with celeriac and pear purée, autumn spring roll (a cylinder of shredded, fried potato filled with offal) and elderberries was declared to be "the best restaurant grouse I have encountered".

If there's one thing Howard can be certain of, it's that Maschler will be only the first in a long line of critics coming to Elystan Street to see what the former two-Michelin-starred chef of 19 years standing does next. "I'm nervous and unbelievably excited about it," says Howard.

Stylish surroundings When they come, what will they find? Certainly not the Square mark two. For a start, the dining room is a far less formal place. Put together by Nelson Design (which is also responsible for the Ledbury), the interior of the light-filled, elegant 64-seat room features contrasting chairs by Gubi in airforce blue and pale salmon, banquettes in teal leather, resin-spun pendant lighting and bare oak and concrete-topped tables. The 14-seat private dining room features a very snazzy white Cortiantopped, adjustable-height table and adjustable stools that will also function as a communal space for customers who want to drop in for a plate of food and a glass of wine.

And then there's the food. In the dishes I sampled, including a wonderfully inventive and dramatic assembly of John Dory with black rice, trompette de mort and butternut squash, the flavours were brought vividly into focus by a rich, fish stock-based jus gras and a wonderfully piquant pickled walnut purée. It showed all the hallmarks of a gifted chef applying his skills, knowledge and talent to pull away from past glories and carve out a new style for himself.

"There's not going to be an all-out radical change, but there will be some stuff that is completely different to anything I've done before," says Howard. He adds that the biggest change will be noticeable on the lunch menu, with the likes of a salad of roasted vegetables with cashew hummus, curry oil and shallots. "I got very ground down at the Square at the end, dealing with all the dietary issues that have become the norm now. The net effect on the kitchen is that it's stressy and not enjoyable, so we really want the lunch menu to be very clean, very pure. There will be very little flour in those dishes, very little dairy, but in a way that I'm hoping people won't really notice."

The change in direction has also been prompted by Howard's increasingly strong feelings about sustainability. "I've stood in kitchens for 30 years, peeling langoustines, scrubbing truffles, opening tins of caviar, sending ceps back if they're not perfect and, in the context of where the planet is, that's quite crass and sits increasingly uneasily in my conscious."

Howard has also been keeping a weather eye on the wider London restaurant scene - especially its younger protagonists. He's even gone as far as investing in chef Ben Marks, formerly of the Square, who will open Perilla in Newington Green, north London, later this year with backing from Howard.

"Before I got involved with Elystan Street, I thought it was a wise thing to look to the future, rather than rely on my own ageing abilities or style, and to try to be quite strategic about it," says Howard. "I've backed one horse and am planning on backing another. These are not financial moves with big expectations; the truth is, I sold the Square and the money is just going to sit and fester in a bank. There are a lot of gifted people out there who don't have the resources to launch themselves, so if you can play a part in people you believe in, that's a really satisfying thing to do."

Although Howard says he has enjoyed meals at the likes of Clipstone (he says a dish of Hispi cabbage, burnt aubergine and pickled elderberries was "magic") and hopes that influences from that new wave of cooking will come through from his new brigade, he remains a self-contained chef.

"I've always cooked very much from within. When it comes to the time to change the menu, I go and lock myself away and think. Of course, I have influences, but I'm not someone who pores over cookbooks or Googles or interacts with other people. I will always stick to the flavour combinations that I've come to believe in because I have to understand what I'm doing. My cooking has always been intuitive and sometimes I see things that dovetail with my natural instincts that are progressive and different and they take me off."

Business brain Unquestionably, the food will continue to evolve as the restaurant matures, with Howard's focus remaining on the kitchen, while Mascarenhas takes care of business. "She's fiercely intelligent, she's a phenomenal businesswoman, she gets things done and helps to generate as good a bottom line out of a given situation as you could possibly hope," says Howard.

"And on top of all that, she's a passionate restaurateur. I've been sort of institutionalised in many ways, having spent such a long time just doing one thing, and I really enjoy having someone else's opinions and input. She's very honest and she speaks her mind. She will be key to the intelligent decision-making and profitability of the business."

Howard readily admits that one of Mascarenhas's hurdles in ensuring profitability will be helping to curb his predilection for flashing the cash - especially, he says, when making money in the restaurant business is harder than it's ever been.

"Rents are a big part of that but the National Living Wage, troncs slowly but surely collapsing, the cost of utilities - the whole thing is against us, but it's still an industry where if you get all the margins right you can still make your bottom line," he says.

In some ways, Elystan Street is Howard's personal phoenix from the flames, a revitalisation following the last days of the Square when he says he "let go" of the kitchen. "Once I'd made myself redundant, I got no fulfilment from the restaurant at all and that was the beginning of the end. I was worried that perhaps I'd lost the sparkle a bit. I'm by no means a complete chef, but when I sit down and think about food, it's a happy place. I think I have a good palate and a fertile mind and that's the most important part of my jigsaw. I've really enjoyed thinking about menus again because I've found that the fire still burns."

Rebecca Mascarenhas on Elystan Street and working with Phil Howard

We're very aware that Elystan Street will be a neighbourhood restaurant as well as a destination restaurant. What makes it neighbourhood as opposed to West End? Repeat business is huge and just being nice to everybody - it's amazing how many restaurants forget that.

Sonny's Kitchen has been a neighbourhood restaurant for 30 years, so we like to think we know about neighbourhood restaurants. This restaurant sits well in this neighbourhood, and we hope that many people who come here will just walk round the corner.

It's a really simple design because over-designed restaurants date and the theatre should always be the customer. We've spent money on chairs that are really comfortable and on lighting, because I think it's key, and we've spent on modern art, which is a big thing for both of us.

One of the reasons Phil and I work well together is that we have the same company culture beliefs. We both want to make it a place where people want to work. Staff retention is very high on our list and the way you do that is by creating a culture where staff are well-treated and respected. We try to be decent human beings rather than flog our staff to death.

I'm also very conscious of green and sustainability issues and of being as conscious as we can be of our footprint. We're serving filtered water and we've knocked a fair chunk off our P&L by not serving mineral water.

The best thing about working with Phil is that I don't have to think about food. We discuss menus, we discuss pricing, we discuss format and I can say I don't like something, but if he says 'No, I think that's right', I will never gainsay him.

The one thing you have with Phil, and very few chefs have it, is actual taste. Phil is a man with views about food. He is an evolving chef, he's not stuck in the past. He has a remarkable ability to make food taste intensely of itself - it's an extraordinary gift.

When we started this project Phil wasn't going to be the chef, but he was so excited by the whole idea that he said he'd like to do it. We're nervous mainly about the expectation of where Phil should be. Being a two-Michelin-starred chef for 19 years is a burden - and I don't mean that in a horrible way. It's a fantastic achievement, but what is the expectation of the press, of his own loyal customers? Are they going to say it's not a two-star restaurant, even though that is not our aim? It's quite nerve-racking.

What's next? We just need to breathe deeply. This is our own money. We turned down a lot of investors - we've never worked with them. We don't have any hedge fund venture capital backing to say we'll do five restaurants in three years, so our growth is purely organic. Do we have the energy, do we have the inclination? Life is for living, not for a bank statement.