It's Called a Cake ... it has the consistency of a cake ... but for tax reasons ... they wanted to call it a biscuit ...
From the free encyclopaedia - wikipedia:
Jaffa Cakes are biscuit-sized cakes introduced by McVitie and Price in the UK in 1927 and named after Jaffa oranges. The most common form of Jaffa cakes are circular, 2+1⁄8 inches (54 mm) in diameter and have three layers: a Genoise sponge base, a layer of orange flavoured jam and a coating of chocolate. Each cake is 46 calories. Jaffa cakes are also available as bars or in small packs, and in larger and smaller sizes. The original Jaffa Cakes now come in packs of 10, 20, 30, or 40, having been downsized in 2017 from 12 or 24 per pack.
Pictured below: On the left (fig.1) is an incorrectly photographed Jaffa Cake stack, a tragic, but all too common mistake. On the right (fig.2) side is the traditional serving arrangement, with the chocolate side down. Everyday is a school day.
Because McVitie's did not register the name "Jaffa Cakes" as a trademark, other biscuit manufacturers and supermarkets have made similar products under the same name. The product's classification as a cake or biscuit was part of a VAT tribunal in 1991, with the court finding in McVitie's favour that the Jaffa cake should be considered a cake for tax purposes. In 2012 they were ranked the best selling cake or biscuit in the United Kingdom.
Please see following links for more information:
Why Jaffa Cakes are Cakes and not Biscuits
VFOOD2660 - https://www.gov.uk/hmrc-internal-manuals/vat-food/vfood6260