"They've been doing it at home since childhood. We use the same cooking methods as they do in their hometowns."

The fish has been a signature dish of In and Out for over a decade.

It's simple yet requires patience, Shi says. The fish is marinated with salt, ginger, cooking liquor and lemon. And lemon grass and other seasonings are continuously added as it's grilled.

"I've cooked Yunnan food during all of my 20 years in the kitchen," Shi says.

"It's fresh and healthy. I hope more people in Beijing can enjoy its authentic flavors."

Yunnan's fare varies by area.

"Take Dehong Dai and Jingpo autonomous prefecture in the west of Yunnan, as an example - the weather there is hot, so the food is sourer and spicier and has less oil," Shi says.

"They use fresh herbs like lemon grass for seasoning."