Green food for St. Patrick’s Day is a purely American tradition — thanks in part to McDonald’s. The chain dyed milkshakes green as a promotion in 1970 and is still cranking them out 50 years later. Shamrock Shakes have developed a bit of a cult following. Fans debate the flavor (it’s officially vanilla-mint, but some insist there’s a hint of lime) and frantically visit multiple locations to get their hands on one. Only certain spots sell them, and only in February and March. If you can’t find one, get your fix with this recipe from our test kitchen.