Make dough: Blend together flour, butter, shortening, and salt in a bowl with your fingertips or a pastry blender (or pulse in a food processor) just until mixture resembles coarse meal with some small (roughly pea-size) butter lumps. Drizzle 3 tablespoons ice water evenly over mixture and gently stir with a fork (or pulse) until incorporated.
Squeeze a small handful of dough: If it doesn't hold together, add more ice water, 1/2 tablespoon at a time, stirring (or pulsing) until incorporated. (Do not overwork dough or pastry will be tough.)
Turn dough out onto a work surface. Divide dough into 4 portions. With heel of your hand, smear each portion once or twice in a forward motion to help distribute fat. Gather all dough together with a scraper (if using) and press into a ball, then flatten into a 5-inch disk. If dough is sticky, dust lightly with additional flour. Wrap disk in plastic wrap and chill until firm, at least 1 hour.
Make pie shell: Put oven rack in middle position and preheat oven to 350°F.
Roll out dough on a lightly floured surface with a lightly floured rolling pin into a 13-inch round. Fit into a 9-inch pie plate. Trim edge, leaving a 1/2-inch overhang, then fold overhang under slightly and press against rim of pie plate. Decoratively crimp. Chill shell 30 minutes.
Lightly prick bottom and side of shell with a fork. Line shell with foil and fill with pie weights. Bake until pastry is pale golden along rim and set underneath weights, 15 to 20 minutes. Carefully remove foil and weights and bake shell until bottom and side are golden, about 15 minutes more. Cool completely in pie plate on a rack, about 20 minutes.
Make filling and bake pie: Whisk together yolks and salt in a bowl until blended, then whisk in syrup and lemon juice. Stir in pecans and pour filling into pie shell, spreading nuts evenly. Cover edge of shell with a pie shield or foil and bake just until filling is set, 20 to 30 minutes. Cool to warm or room temperature on rack.
Cooks' note: Pie can be made 6 hours ahead and kept at room temperature.