Shop owner Tran Khac Tuan said he is happy that the bread was so warmly embraced and their orders quickly increased. Tuan’s shop sells 300 to 500 loaves daily.

"It took us about a year to research the right recipe and four testings for the bread," Tuan said. "Hanoi, Danang and HCM City have their own distinctive foods so we also want to make something for Quang Ninh."

The bread is made with bamboo charcoal powder and squid ink. Squid represents the coastal areas while charcoal is a symbol for the numerous coal mines in Quang Ninh. Tuan said they only use seafood for the toppings, including shrimp, squid and crab, as they hope to give everyone an affordable meal with seafood.

Each sandwich is sold for VND25,000 to VND45,000.

Thuy Trang, a customer in Hanoi, said that after hearing about the bread from her niece she had travelled to the shop to try the bread. Trang said both the look and the taste were very nice.

"I was curious about how the bread looks and tastes in real life. I also bought five to six more loaves for my nieces and nephews," she said.