Fair trade, single origin chocolate. It will often say the farm it's from on the packaging and everything. It's often much more expensive, of course, but it also tastes much better :).

It's mostly because it's almost impossible to make that guarantee (honestly, at least), even if you're really actively trying to vet your supply chain. There just isn't much child-labor-free cocoa production in the world period, and there's a lot of structural forces on the ground keeping it that way.