Firewall is described as a theatrical operation featuring a dark room with flames and sizzling dishes, costing about £12 per head for a two-course meal.
Mustard wants to incorporate Firewall in 41 Brannigans by the end of the year.
It currently has 16 and the concept will be included in all Brannigans as well as a stand-alone Firewall in Aberdeen, Scotland, in the Queens Link Leisure Park. More stand-alone sites will open if successful.
The first Firewall opened in February in Reading, Berkshire, and another 15 will open this month.
The Brannigan's in Stockport, Cheshire, has a smaller version, Firewall Metro.
Another two Brannigans are being built in Warrington and Norwich and seven acquisitions are planned this year with another 10 in 2002.
Mustard hopes sales will reach £44m by the end of this year with food sales accounting for 7%. Turnover is currently£34m with food sales accounting for 3%.
Brannigans has historically treated food as a necessary evil to get a drinks licence.
Mustard Entertainment bought the chain for £69m along with three pubs in Scotland and several theme sports bars seven months ago.