In a large mixing bowl mix the dry ingredients and add the butter and egg yolk, have a cup of ice-cold water with a tablespoon ready but don't use the water yet!
Start to incorporate the butter and flour mixture together until it has a crumble like consistency / the consistency of wet sand.You can do this by hand or using a food processor
Now add a tablespoon of water at a time until the dough starts to come together. I normally use about a quarter of a cup but, every time you make this the amount of water will probably change, so go slow and steady
Place the dough onto a clean surface and knead with a bit of flour until the pasty is not sticky and well combined and soft and form into a round discWrap in cling film and chill in the fridge for at least an hour
Take the pastry out of the fridge 20 - 30 minutes before rolling out