Wagyu smash burgers land at BŌS Burger in MSA Annex

BŌS Burger (pronounced “boss burger”) celebrated its grand opening on Monday, December 8, at the MSA Annex of the Mercado District. Duo Michael McCormack, owner of nearby Japanese restaurant Kukai, and Akiko Senda, owner of nearby florist and boutique shop Bloom Maven, both own BŌS Burger.

The restaurant operates at 267 S, Avenida del Convento in the shipping container which previously housed Beaut Burger. While Beaut Burger previously indicated their replacement restaurant would still serve Beaut vegan patties, that is currently not the case and BŌS Burger has no affiliation with Beaut Burger, McCormack said. They are working on developing their own vegan recipes, which are not available quite yet. However, they currently offer a vegetarian option.

A tight menu built around Kobe American Wagyu

The name pays homage to Japanese brand Suntory BOSS Coffee and to the Bos taurus genus of cattle, also known as wagyu. The menu’s smash burgers use patties made from Kobe American wagyu beef, which McCormack said comes from a cattle rancher that brought full-breed Kobe to the United States for ranching. The lower melting point of wagyu fat leads to a silkier mouthfeel compared to fat from other forms of beef.

While the restaurant itself isn’t Japanese, influence from Japan comes through via the Japanese Buta Katsu Sando, Japanese Kewpie mayonnaise, and the shiitake mushroom salt used to season the burgers.

Guests choose single or double patties, or swap in a veggie patty, with prices starting at $11. The burgers come on Martin’s potato rolls, a soft and squishy East Coast favorite.

Menu Highlights

• Classic Smash Burger – wagyu patty with American cheese, diced onion, lettuce, tomato, mayo, and pickle.
• Fried Onion Burger – thinly sliced onions grilled into the wagyu patty, American cheese, house Dijon aioli.
• Green Chile Burger – wagyu patty with, roasted Hatch, American cheese, house and Dijon aioli.
• Buta Katsu Sando – hand-breaded pork cutlet, Kewpie, tonkatsu sauce, and cabbage.
• Fries – shoestring potatoes fried to order.
• Shakes – chocolate or vanilla.
• Soft Serve – chocolate, vanilla, or swirl in a cone.
• Hidden Hearth Cookie – chocolate chip, baked a few doors down.

Incoming cocktail bar

Locals can also look forward to an attached cocktail bar concept, Bozu Bar. However, the concept is still in its early stages with a projected opening of autumn 2026.

BŌS Burger is located at 267 S. Avenida del Convento. Operating hours are 11 a.m.-9 p.m. daily. For more information, visit bōsburger.com. Keep up with BŌS Burger on Instagram.