Preparation

• In the bowl of a food processor, pulse the flour, salt, and sugar. Add butter and shortening and pulse until coarse, pea-sized crumbs appear, about 10 seconds.
  With the machine running, add vinegar and 1/4 cup ice water and process until the dough just holds together, about 30 seconds.
  Squeeze a small amount of dough between your fingers and if it is very crumbly, add more ice water, 1 tablespoon at a time (2 tablespoons maximum). Do not over process.
  Turn dough out onto a lightly floured surface and push together into a rough ball.
  Knead a few times to combine, then divide into two equal balls.
  Flatten each ball into a disc with smooth edges, cover with plastic wrap, and refrigerate at least 1 hour or up to overnight.