She's showing me around her new place, 11 Abingdon Road in London's Kensington, which opened at the end of October. Or rather, she's showing me the art that she and her husband have bought for its walls. There's a sketch by Picasso, a Jim Dine and a small oil by Lowry, plus a gorgeous sketch of a porcupine. "I picked that up in India," she says.
This is Mascarenhas's fourth restaurant, after Sonny's in Barnes, Sonny's Nottingham and the Phoenix in Putney - "a successful formula of food with a modern sensibility, served in stylish surroundings", declared the London Evening Standard restaurant critic Fay Maschler earlier that morning (it was a great review). Not that she ever planned to have more than one restaurant. "It's been an organic growth," she says.
The chef is Australian Greg Blampied, who is ex-Sally Clarke; the manager, Ian Powrie, former Groucho Club and People's Palace. So why Kensington - this is a bit more central than the other two? "The guy who used to own it approached me three years ago, but the price wasn't right - until now. And Kensington is a great neighbourhood," she argues.
Choosing a great neighbourhood location is one of Mascarenhas's strengths and it's partly why her business has been so successful. It's nearly 20 years since she opened her first place, Sonny's - "Oh God, is it really that long ago?" - which is still going strong; and, apart from the odd bum venture, things couldn't be rosier.
Other projects She has even started investing in other restaurant projects that she believes have got the right formula - most recently Sam's Brasserie and Bar in Chiswick, west London, fronted by Sam Harrison, which she bankrolls along with other backers, notably Rick Stein.
So it comes as no surprise to discover that her knack for finding great restaurant locations has been extended to other property ventures. Mascarenhas and her husband, James Harris, boast a property portfolio that, well, means that the bank doesn't get involved so much any more. "I've been very lucky. I haven't had to borrow any money for this place. Though I'm quite prudent," says Mascarenhas.
Not that it's always been such plain sailing. When she opened Sonny's, her first child, now 17, was often left behind the bar in a basket while she got on with the business of running it. It was the late eighties, and the London restaurant scene was just taking off. Alastair Little had opened, so had Kensington Place, though there wasn't much around in the way of today's neighbourhood restaurant (ie, modern European). "I was particularly impressed by Alastair's. It had simple food, cooked well, in relaxed surroundings, with no pomp."
The Union Square Café in New York was another source of inspiration. "I knew that I didn't want a special-occasion restaurant. I like going to places that are comfortable, where you want to eat every day, with well-sourced food. That's my key interest today, even more than cooking," she says.
But we're jumping ahead here. Did she always want to own a restaurant? "You're joking, aren't you? No one suggested a career in catering when I was growing up," she laughs. She fell into it, like a lot of people. Her acting career didn't really take off - "I was terrible" - so she took up waitressing, working at the Chicago Pizza Pie Factory with the legendary Bob Payton.
Then she opened the Rib Shack in Knightsbridge for Payton, as general manager. It was about this time that she decided she could make a career of it. "It's a great industry because there's no clear path; you can be a chef or front of house. There are lots of roles. Yes, it's one of the most demanding industries, but it combines two things I love: food, and my innate organisational skills," she says. Not that her parents approved. Immigrating to the UK from Kenya in 1967, they saw their daughter in what they thought were far more solid professions, such as banking or law.
Playboy Club There was a brief stint working with Claudio Pulze; then she hooked up with another London legend, ex-Playboy Club boss Victor Lownes, running the restaurant at the Stock's Club in the King's Road, eventually ending up a managing director. "I particularly enjoyed learning about the financial side of the business. I was fortunate to work for such an entrepreneurial man," she says of Lownes, whom she still sees.
She turned things around, but it wasn't easy at first. "The staff gave me a tough time to begin with - speaking to me in languages I didn't understand; screwing around with the till system so it didn't add up at the end of the day. I don't blame them entirely. Some of them had been waiters there since the sixties, and here I was, this tough young woman. I don't think I realised the challenge at the time, but I'm reasonably determined," she says, modestly. When Lownes turned down her request for a bigger cut of the business, she decided to leave and do her own thing.
Cue Sonny's. "This polished neighbourhood restaurant has been satisfying the culinary appetites of Barnes locals for years," credits the Time Out guide. The menu now includes dishes such as salad of smoked quail and aubergine with pomegranate jus (£8), gnocchi with fresh tomato, garlic, capers, basil and toasted pine nuts (£7.50/£10.50) and pan-fried skate wing with parmentier potatoes and brown shrimp dressing (£13.50). The wine list is well chosen and concise, at 75 or so bins, with plenty to choose under £20, though the average spend is much higher.
And, as Mascarenhas was saying earlier, she reckons sourcing good produce is a key to her success. "I work closely with my chefs on this. It's generally me who is spotting new things at farmers' markets or finding things in magazines. I like to keep abreast of what producers are up to," she says. "I have no qualms about putting on ingredient-led dishes. I wouldn't say that technique is nothing, but if you've so disguised something that you can't taste it, I can't see the point," she says.
I bet your chefs love you for saying that. "I say to them that I'm your eyes and ears on the floor. I'm your editor. Editors fine-tune and put the creative force into a manageable form. If Graham Greene can work with an editor, so can you." Nice answer.
She even opened a food shop in 1991, next door to her Barnes restaurant, to spread the word about her produce further - "though I'm not a natural retailer", she admits. As a deli it lost money, but when she expanded the restaurant into the next-door property and incorporated the shop into the restaurant space, giving it more of a traitteur focus, things started to take off.
"The restaurant already had a reputation, and when people saw that the daube of beef that we were offering in the shop was cooked in the restaurant, they went for it," says Mascarenhas. Now, the Phoenix gets involved with supplying dishes, and so will 11 Abingdon Road once things settle down after the launch.
Three years after Mascarenhas opened Sonny's in Barnes, she opened a branch in Nottingham. Does she have family ties in the city? "My brothers were at university there, and I loved visiting and wanted to open a second restaurant; but interest rates were soaring in London, so I decided to do something outside the capital," she explains.
Nottingham, however, wasn't quite ready for it in 1989. "They couldn't get their heads around wooden floorboards and menus written in English," remembers Mascarenhas, who decided that this was a good time to have her second child. She has three girls now.
"I'm a great champion for women's rights. I think the Government makes it very hard for women to get back to work after having children. There are still very few women-driven enterprises. I'm not saying I'm Superwoman or anything - I have a nanny and a support network.
You have to. I try not to do eight million things at once, but I still have to be there to help my kids with their homework. It is part of my role as a mother, and I love doing it."
Perseverance The recession lasted well into the 1990s, but she persevered with Nottingham - though she did try to sell it a couple of times - serving good food at reasonable prices and with friendly service. "It worked out in the end," she says. She still travels there to check up on things every week or so.
She applied the same formula to the Phoenix in Putney, which opened in 1996. When it lost momentum four years ago, she asked Italian master chef Franco Taruschio to consult on the menus. "He helped us to refocus," she says, and the Phoenix has since successfully adopted a more Italian slant, with a little help from chef Roger Brooks, who worked with Taruschio at the Walnut Tree Inn in Abergavenny. Your staff seem to stick around - you must be a nice boss? "I'm fair," she says, carefully. "And I'm a person of my word."
Now the closures. What happened to Parade, the restaurant she opened in Ealing in late 1990, which was well-received by both critics and customers? "I got an offer I couldn't refuse," she grins. La Tasca now owns the site.
Then there was Bibo, with its wood-fired oven turning out top pizza. "I'm not sure why that didn't work - I guess it was the location. It certainly wasn't the food. I personally thought it was fantastic. I was very proud of it. But I'm not so rose-tinted about my own product. It went under because it was rubbish," she shrugs.
So what's next, and what's with Sam's? "Actually, I interviewed Sam for a job initially, but he couldn't give me his total commitment because he wanted to open his own place. Then, when I heard later he was having financing problems, I stepped in and helped out. He's terrific," she says.
"People have been very good to me in my life and, of course, hopefully, it will be a sound investment. I think this is the way forward for me - doing more things like Sam's," she adds, revealing that she is already looking at another investment with "a high-profile chef". But that's all she's saying for now.
Neighbourhood wines Mascarenhas gets irritated by restaurants that don't offer enough wines by the glass - I counted 26 by the glass on the list at 11 Abingdon Road. "And I always want something interesting to drink," she says.
The list boasts the likes of Picpoul de Pinet from the Languedoc (Feline Jourdan); dry Riesling from Germany (Burkin Wolf); Clare Valley Riesling (Skillogalee); Tuscan Chardonnay (Isole e Olena); New Zealand Pinot Gris (Huia); Aussie Pinot Noir (Shadowfax); and reds from up-and-coming Spanish DO, Jumilla (Casa Castillo).
She leaves the wine selection up to her husband, James Harris, who works with 10 suppliers, including Bibendum, Liberty, Les Caves de Pyrene and Loeb. "What I'm looking for is upfront, but clean front - an immediate yumminess," says Harris, who lowers the mark-ups the higher up the list you go and boasts an average spend of £29 a bottle.
The list at Abingdon Road is a work in progress, he says, but it will never be more than 75 bins. "You don't sell any more wine if you have 500 on the list - and long lists are intimidating. By keeping the list small we can change it frequently. We have so many regulars, they want to see new wines. And we like to change the list to suit the seasons," he says.