In the lush province of Esmeraldas, on Ecuador's northern border with Colombia, farmers are proud to say they produce "black gold".

They are not talking about oil, Ecuador's main export, but cocoa beans.

The smooth, bitter-tasting paste extracted from the beans is the key ingredient in chocolate and one of this Andean country's claims to fame.

It is also deeply connected to the history of Ecuador, the world's largest exporter of cocoa until the beginning of the 20th Century.

Plant disease and the rise of new cultivations in British and French colonies across Africa and Asia saw Ecuador lose its top spot in the early 1900s.

Cocoa started losing its appeal to farmers and was replaced by bananas and coffee, which were more lucrative.

West Africa became the world's leader in cocoa production and exports, with a focus on so-called "bulk" or "ordinary" beans, used for processed chocolate-flavoured candies and sweets.