Rohan Barnett was backpacking his way through Mexico when he saw something that changed his life: cacao, the magical seeds that become chocolate. The elliptical pods dangling from small trees seemed impossibly far removed from the foil-wrapped squares he knew back home in Ireland.

Barnett was surprised to learn that the Mayans had been growing cacao long before Europeans arrived, and that they drank it as a cold beverage with a spice called annatto, which turned their mouths red.

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