The 50-cover Woodland Kitchen is scheduled to open in Penshurst, joining the group's established restaurants The Swan Wine Kitchen at Chapel Down vineyard in Tenterden and The Twenty Six and The Beacon in Tunbridge Wells.
I'll Be Mother creative director Scott Goss, who is also head chef of The Twenty Six, told BigHospitality the restaurant would have its own style, but could reveal no further details.
"Everything is being finalised. The floors are being laid and the tables are about to go in, but it won't open until Peter (Cornwell, I'll Be Mother owner) is happy with it," he said.
"It's a beautiful restaurant right at the top of Seven Trees in Penshurst. We're looking for a very organic style there, but I can't say what will be on the menu because I don't know yet."
Cornwell and Goss created I'll Be Mother in 2014 after working together at Cornwell's pub The Swan in West Malling where Goss was head chef for three years.
The Beacon, a restaurant set within 17 acres of land in Tunbridge Wells opened in 2014, followed by Twenty Six, a 26-cover 'test kitchen' where Goss aims to 'connect people' through sharing, not serving. The group also includes an events business called Mother Love and a food truck called Mother Truck.
"We're not a chain. Everything we do is unique. We've been established in Kent for many years and just like to do things organically," said Goss.