Sift flours into a bowl and rub shortening through until crumb like.
Alternatively put flour into a food processor and blitz shortening until crumb like.
Add sugar and mix in.
Add lightly beaten egg yolk and water to the dry ingredients and mix to a dough. Cover and set aside in the fridge for 15 mins or so to make rolling easier.
Notes
Can freeze this dough, cling film with no air and a sealed bag. I divide into 2 or 3 portions.