The newly refurbished Frangoz restaurant and takeaway in King Cross made the offer to the first 1,500 customers through the door who ordered a burger and chips.
Long queues began to form from 10am, two hours ahead of the grand opening on Saturday.
Adam Khan, the manager of the Halifax branch, said: "We had massive, constant queues since 10am all the way up to 11pm.
"We served well over our initial 1,500 meals cap, to around 4,500 meals but we kept it well organised.
"With Covid-19 it has been a stressful time for the local community so we wanted to bring the community spirit together and give something back ”
The company is also using the franchise model to expand nationally and locations have been secured to open outlets in Sheffield, Glasgow, Manchester and London