Every family has its secrets, some more closely guarded than others. The margarita recipe at the Fort Worth, Texas, restaurant Joe T. Garcia's has been one of the closely guarded ones for almost 80 years, and even celebrity chef, investor and fan Tim Love will never find out what it is.
The restaurant was founded in 1935 by second-generation owner Joe Lancarte's grandparents. They did so with the most threadbare of aspirations, serving 16 customers a night in a single room with four tables.
Read More Taking on Starbucks, one cup at a time
Today, Joe T. Garcia's has grown into a sprawling attraction with multiple rooms that can serve over 1,000 people a night. According to Lancarte, this is because his grandparents understood how to run a family business right from the beginning, and they passed that know-how down to the next generation.
"We've always believed in hands on, we like to stay hands on and control and watch everything that goes on in our kitchen," he said. He also noted that the restaurant's steady growth is the direct result of slow expansion.
"We're afraid if you grow too fast, too quick, then you can't handle what comes into the room," he said. "That's not a good thing."
Read More One-dish restaurants: Just a fad?
He added that the restaurant's simplicity has been an important factor in its growth.
"Back in 1935 when my grandparents started, I think we served a bowl of chili—one bowl—and just stayed one dinner," he said, "There's still just a small menu, actually no menu, which you know. It simplifies it. It makes it easier on our kitchens and we're able to get the food out there for the masses."
Read More Will farm-to-table work in Texas?
Tim Love agreed that the slow and steady approach of the restaurant's generations of owners was the key to its success.
"What I find unique about Joe T's is you guys started as a 'we serve dinner' shop," he said. "You see restaurants grow from one concept, and then they want to go out and do 30 of them around the country. It feels like Joe T. Garcia's took a different path…. It's an institution here, and if you want to eat Mexican food, or have some of the best margaritas, you come here."
Read MoreSigns that you're in a bad restaurant
—By Liza Hughes, special to CNBC
"Restaurant Startup" is on a quest to discover, invest in and launch America's next generation of epicurean superstars. Tuesdays at 10 p.m. ET/PT.