The Parisian group will open Gloria, an Italian trattoria 100% staffed by Italians, in Shoreditch.
It will source 180 ingredients imported direct from Italy and make Neapolitan pizza, fresh pasta and gelato every day.
Victor Lugger, who started the group with Tigrane Seydoux, six years ago, admitted: “If tomorrow there is a very bad Brexit, yes, everything I do will fall apart.
“We are probably the least Brexit-compatible restaurant in the UK starting Friday. I’ve been extremely brave or extremely stupid maybe.”
He says he is “quite optimistic” about Brexit but “whatever happens…you still have 10 million people in this city passionate about food and vibrant places.
“I think with the offer we’ve got…the products are probably the best you will find in London at a very affordable price. That, I think, is a restaurant that works with Brexit…we try to be a vibrant authentic place."
The 165-cover restaurant is designed to make customers feel “when you pass through the door you are in Italy for an hour or two”, says Lugger.
Furnishings and other materials have been purchased from antique shops all over Italy.
“I think our biggest challenge is there are many places where you can eat amazing Italian food here in London,” says Lugger, which is why the focus on authenticity is key.
The menu includes Big Sharers for two, priced at £16 per person for La Gran Carbonara and £35 per person for a Florentina Steak Cut. There are also dishes that can be shared between four people, such as the 10 Level Lasagna for £48.
Starters are priced from £4 and Pizzas from £11. Vegetarian and vegan options are available.
Big Mamma owns Paris restaurants East Mamma, Ober Mamma, Mamma Primi, BigLove, Pink Mamma, Popolare and La Felicita - an Italian food hall with 1,500 covers.
The group has earmarked another site for a different format in London's Fitzrovia. “We don’t have a five-year plan,” says Lugger. “We do restaurants because we love them and every project is a new adventure and it allows us to break new ground from our perspective.
“I have no clue as to how many restaurants I’ll do here. Right now I’m thinking how can I give the people who come to my restaurant the best time...that’s why I founded a restaurant business and not a private equity business.”