Retired pastry chef: Advice from my mother and grandmother- keep every ingredient as cold as possible and handle the dough minimally, just enough to bring it together.

Experience taught me: Use all butter or combine shortening and butter with vodka as the binder from Cooks Illustrated.

Important: wrap the dough discs in plastic and rest in freezer or refrigerator for at least an hour but better overnight.....resting covers a multitude of sins...I make my dough in the food processor, 1st dry pulsed, then shortening pulsed in lightly, then frozen butter cubed pulsed in to large pea size, then vodka pulsed in until just holding together.(do not over work), then make into discs, wrap, refrigerate/freeze and rest......It ALWAYS works well.