For pastry: cut cold butter into 1-inch squares. Place butter and shortening in food processor bowl with blade. Add dry ingredients and pulse until the butter is the size of small peas. Turn flour mixture into a large mixing bowl and drizzle with 2 tablespoons ice water. Toss the mixture with a bowl scraper to moisten the dough.
Keep adding water 2 tablespoons at a time until a handful of dough, when squeezed, will hold together. All of flour mixture should be absorbed, but not too wet.
Take a handful of dough and smear across a cool countertop. Scrape up, and stack, treating the remaining dough a handful at a time with the same process.
Press together and wrap tightly with plastic. Chill for ½ hour.
On a lightly floured surface, roll half of the dough into a large circle, ¼-inch thick, and press into a 9 inch deep dish pie pan. Trim top edge with ½-inch overhang. Fold over and crimp, or stamp with a fork.
To make filling: lightly toast pecans, reserve to cool on pan. Whisk eggs with sugars until smooth, then add the syrups, bourbon and sea salt. Place 1½ cups cooled pecans in the bottom of each prepared pie crust then pour in enough filling to come within ½-inch of surface.
Place pies on cookie sheets on bottom rack of 350º for 30 minutes. Reduce heat to 325º and cook until center is firm. If you see tiny bubbles or steam coming from the center you can bet they’re done.
Cool completely before serving. Overnight is best, and the trick is to invert the pan on a cutting board to slice the pie upside down. Then invert onto serving plate very carefully. Just commit and everything will go just fine!
Makes 2 9-inch pies.