High-fives are part of Mulberry and Vine's philosophy. As the company explains on its website: "Our mission is to promote happiness, and we believe the high five is magical in supporting that. The physical act of the high five releases dopamine, which is the feel-good chemical in your body.  And try not to smile when someone gives you a high five. We've tried. Not possible."

Another Mulberry and Vine's philosophy "is to get more vegetables on people's plate," said co-founder Justin Schwartz. "We use the highest quality of ingredients we can find. We don't cut corners."

Mulberry and Vine uses a commissary kitchen for prep work but still cooks at each restaurant.

"I think one of our big differentiators is transparency," said Schwartz. "We list every single ingredient on our website and on our menus. No one else doing that."

The Mulberry and Vine menu has options for diners on the most popular diets of the moment — gluten-free, paleo, ketogenic. "Everyone feels happy," Schwartz said.

The charred avocado (center) is one of the chain's most popular dishes.

"I owned a women's clothing store and a furniture store in past lives,” Gauthier said. “The design of a space is so important, and I think fast-casual for a long time ... that was just an afterthought.”