Smashburger is making St. Patrick’s Day a little luckier (and sweeter) for hungry bargain hunters. To mark the green holiday, the popular hamburger joint is promoting its OREO cookie mint shake — made with vanilla Hagen-Dazs ice cream, milk and crushed mint OREO cookies. Customers (aka “Smashfans”) wearing GREEN can get a buy-one-get-one FREE OREO cookie mint shake today, Thursday, March 17 at participating locations. It doesn’t get much better than sitting down to a juicy burger, fries and a shake.