First, I want to say (or rather ask) - "Shortbread"?!
The rhubarb filling makes a nice contrast with the sugary, buttery cake. I find this shortbread to be very intensely sweet - good as a small slice with a cup of coffee.
The method was definitely interesting (freezing the dough and then grating it!). It looked more like grated cheese than cookie dough:
|Spreading rhubarb filling on lower layer of grated dough|