Thus far, I’ve only encountered these in a pack of four assorted tarts, so am not entirely sure they are specific to Scotland. Vague snippets of information on the internet seem to support the theory, but until I see them more widely available, I’m going to reserve judgement.
The name, I assume, come from the fern-like decoration in chocolate atop the icing of the tart. The tart itself comprises a pastry shell, a thin layer of red jam, a cake layer and an icing topping. It is very similar to a Bakewell tart, without the addition of almonds.
As I’m not really that fond of Bakewell tart, fern tart was not for me. However I am going to keep a sharp eye out for other versions in bakeries, as I’d be interested to have another try.