Mars, Nestlé and Hershey pledged nearly two decades ago to stop using cocoa harvested by children. Yet much of the chocolate you buy still starts with child labor.

Five boys are swinging machetes on a cocoa farm, slowly advancing against a wall of brush. Their expressions are deadpan, almost vacant, and they rarely talk. The only sounds in the still air are the whoosh of blades slicing through tall grass and metallic pings when they hit something harder. 

Each of the boys crossed the border months or years ago from the impoverished West African nation of Burkina Faso, taking a bus away from home and parents to Ivory Coast, where hundreds of thousands of small farms have been carved out of the forest. 

These farms form the world’s most important source of cocoa and are the setting for an epidemic of child labor that the world’s largest chocolate companies promised to eradicate nearly 20 years ago.