Choco-Leibniz is a chocolate biscuit, which bears the slogan 'More chocolate than a biscuit', which I find rather confusing. It reads like a slogan translated from another language (presumably German) to English, by someone with an imperfect grasp of one or both languages. One way of interpreting the claim is that it means:
"More chocolate than a[nother] biscuit"... i.e. that Choco-Lebinz offers a more generous proportion of chocolate-to-biscuit than lesser alternatives such as the humble McVities digestive or Hob-Nob, and such a claim is certainly true. Another interpretation offers an even bolder proposal; it is arguable that the slogan means to imply that Choco-Leibniz is:
"More [a] chocolate than a biscuit"... i.e. that the aforementioned chocolate: biscuit ratio is indeed so prodigious that technically the product must be classified as chocolate, rather than biscuit. But that's just silly, it's clearly a biscuit. It's on the biscuit shelf in the shop, and everything.
The clue to solving this apparently intractable riddle perhaps lies in the biscuit/chocolate's name, so we must look to the works of celebrated 17th-century German philosopher Gottfried Wilhelm Leibniz for an explanation. In his 1685 Discourse On Metaphysics Leibniz introduced his famed 'predicate-in-notion' principle, which claims that every single predicate of a true contingent proposition is contained within the terms of that proposition. If we apply this to the proposition "[Choco-Leibniz is] More Chocolate than a Biscuit", we can see that the predicate 'chocolatiness' is indeed contained within the notion of 'biscuitiness' - that is, that the idea of a biscuit logically contains the possibility of a certain degree of chocolatiness. And yet there is a contradiction, precisely because of the claim that the chocolatiness of Choco-Leibniz is higher than the degree of chocolatiness permitted by the concept of 'biscuit'. Paradox inevitably ensues.
Clearly the makers of Choco-Leibniz are on very shaky metaphysical territory. Perhaps they would have been better advised to seek inspiration for their slogan in another of Leibniz's theories, the idea that the world as it exists is, despite the existence of imperfections, suffering and evil, the optimal of all possible worlds that God could have created. Thus we get:
"Choco-Leibniz: The Best of All Possible Biscuits"
Which, actually, it pretty much is. They're very chocolatey you know.