In a large bowl, mix together 150 grams flour with sugar and salt.
Cut the cold, unsalted butter into small chunks (about 16 pieces per stick of butter) and add to the flour mixture. Using a pastry cutter, cut the butter into the flour mixture until all of the butter is moistened by the flour and forms into a thick paste (see pictures in the recipe post).Alternatively you can use a food processor or press the chunks of butter with your fingers and flatten them to help combine them into the thick paste. I've also had success grating the butter with a cheese grater into small flakes and mixing that way.
Add the remaining 175 grams (1 ¼ cup) of flour and use the pastry cutter or your fingers to distribute the flour until the mixture looks crumbly.
Pour the chilled sourdough discard on top of the flour/butter mixture and stir to combine. Use your hands to form the dough into a ball. If the dough is too crumbly, add ice cold water a Tablespoon at time until it comes together.
Cut the ball in half and form two balls of dough. Wrap the balls in plastic wrap, press down on them to form a disc shape and stick in the refrigerator to chill. Chill the dough for 20 minutes if using right away or for up to 3 days if using later. Wrap and freeze for up to 3 months. Use according to pie recipe directions.
