HOW TOIn a large bowl, stir the flour, salt, and sugar together in a large bowl. Add the butter pieces and mix together well. Combine the water, cider vinegar, and ice in a small bowl. Sprinkle 2 table spoons of the ice water mixture over the flour , and mix until fully incorporated.
Add more ice water, only 1 or 2 spoons at the time, mixing gently until the dough come together in a ball – you will not need the whole iced water you have- leaving some dry bits. Squeeze and pinch with your fingertips to bring the mixture together and combine.
Shape the dough in 2 flat discs wrapped in cling film, and refrigerate for at least an hour, preferably overnight.