When the two brothers behind Peninsula mini-chains Truffle Poke Bar and Guapa’s Mexican Grill were offered a third space next to their two restaurants in South San Francisco, they said yes.

They didn’t know yet what they’d put there, so started brainstorming a new brand to fill it. Ultimately, they decided the space would offer craft sandwiches that couldn’t be found anywhere else, says Naji Haddad, who owns the shop with his brother, Rafi Haddad.

They developed the menu — which offers breakfast sandwich options, plus a set of about 15 lunchtime sandwich options and all-day dining hours — alongside open-face arrangements, salads and more. Each sandwich uses bread sourced from San Francisco’s Panorama Baking adding a satisfying crispy-on-the-outside, chewy-on-the-inside texture.

Bluegrain Sandwich Market in South San Francisco opened in early March with a wide array of sandwich options — including breakfast ones. (Courtesy Yunus Emre Cakir) 

When trying to figure out what to name their new venture, they did some consulting with ChatGPT, Naji says. That’s how Bluegrain Sandwich Market was born. And decorating the space with blue trim around the interior of the shop helped to tie it all together.

Since opening in early March, the sandwich that’s become their most popular is the “The Godfather,” ($18.25) Naji says. The three-meat creation has mortadella, ham, salami, plus pepper jack cheese, onion, tomato, lettuce, smoked pepper, citrus dressing, hot honey and pepperoncini aioli. Customers get to choose their bread (Naji recommends the rosemary focaccia) and whether to toast it or not, among other customizations. For vegetarians, the burrata sandwich ($13.50) uses burrata instead of mozzarella in an otherwise caprese-styled sando, with fresh runny cheese bursting throughout every bite.

Details: Open daily 7 a.m.-7 p.m. at 101 Oyster Point Blvd #105, South San Francisco; bluegrainsandwich.com.