To make the base, combine flour and cornflour in a medium bowl. Rub the butter in until the mixture resembles breadcrumbs. Add the sugar and keep mixing to form smooth dough. Wrap in plastic wrap and put it in the refrigerator for 30 minutes.
Preheat the oven to 180 degrees C. Roll the dough out to line a 20x30cm baking tin. Bake for 10 to 15 minutes, or until golden in colour.
Meanwhile, make the topping by whisking the cream, sugar and eggs together in a large bowl. Add the flour, lemon rind and juice and continue to whisk until the mixture is smooth.
Remove the cooked shortbread base from the oven and - immediately - pour the lemon cream mixture on the top of it. Return to the oven and bake for another 25 minutes, or until the topping is set.
Remove from the oven and leave to cool completely before slicing and serving.
Great recipe - I added a Tbsp of lemon zest to the dough portion for extra *zing*. I had some dough left after rolling it out for the pan, and baked it as normal shortbread cookies. Delicious! - 20 Nov 2011