A Choco Pie is South Korea's equivalent of a Moon Pie: cookie with a marshmallow, covered in a film of bad chocolate.
They're made by the South Korean food giant, Lotte. And yet, they've become legendary in North Korea, too.
The answer runs through the Kaesong Industrial Complex. The Kaesong factory sits near the DMZ between North and South Korea.
There are about 50,000 North Korean workers there, managed by 800 staffers from South Korea.
The managers can't offer cash bonuses to their workers — that's deemed too capitalist by the North.
So, for workers who are especially productive, managers have come up with an informal reward system.
They offer instant noodles and or instant coffee but the gold standard incentive is Choco Pies.
The workers who can score these treats can quietly resell them in the North for three to four times the original price.