Step #1 Sift dry ingredients together In a large-ish bowl.
Step #2 Cut the butter into small chunks (about 1/2" thick) & add to dry ingredients.
Step #3 Work it into the dry ingredients using a pastry cutter or your finger tips, mashing until the butter has crumbled into pea-size pieces.
Step #4 Make a well in the dry ingredients.
Step #5 Pour the egg & apple cider vinegar into the well, & use a fork to stir carefully, outwards from the center.
Step #6 Once all the ingredients are incorporated, drizzle the ice-cold water into the mixture very slowly, just a little at a time.
Step #7 Only add water until the mixture has become a cohesive ball of dough that's just moist enough to handle without being wet.
Step #8 Place ball between two large pieces of parchment paper.
Step #9 Using hands or rolling pin, equally in all directions, carefully push the dough outward, until it is a pie-sized thick, even disc of dough.
Step #10 Leave between parchment paper layers & seal well in plastic wrap or ziploc bag.
Step #11 Refrigerate for at least two hrs.
Step #12 Remove the dough from the refrigerator & allow to sit at about room temp for 15-20 mins.
Step #13 Leaving the dough in between two parchment paper layers, roll it out carefully, as thin as you can.
Step #14 When the dough is between 1/4" & 1/3" thick, remove the top layer of parchment & even out the edges of the crust.
Step #15 Place a pie pan with the top side down over the dough (centered) & then carefully flip paper, dough & pan over so that the dough drapes into the pan.
Step #16 Carefully peel away parchment.
Step #17 Use your fingers to make sure the dough touches all the corners of the pan.
Step #18 If any holes have already formed at this point, mend them with a finger or pastry brush dampened in egg white or water, or with excess dough.
Step #19 Use in your favorite pie recipes, or roll out for use in a galette or other pastry.
Step #20 You can prebake this crust if you like, but it doesn't require prebaking.