On a normal day, thirsty revelers easily drain two kegs of Guinness at Boston’s Black Rose tavern. Come St. Patrick’s Day – an official holiday in Bean Town – and they’ll plow thorough 55 kegs.

“It’s pretty crazy over there,” said Keenan Langlois, corporate chef for The Black Rose and the seven other restaurants in Boston’s Glynn Hospitality Group. “People start early and spend all day there.”

And these days, not all of that Guinness is going down parched gullets. With what he says is the largest Guinness account in the state of Massachusetts, Langlois figured it was time to use it as an ingredient in food, too. His Black Rose burger stacks prime beef with Irish bacon, shredded cabbage and Guinness-spiked ketchup. And he’s not alone.