In a food processor, combine flour, salt, and sugar until blended. Add shortening and butter until it resembles coarse crumbs, then gradually drizzle in ice water until the dough forms a ball.

Remove dough from processor and divide in half. Roll one half to 1/8 inch thick, place in pie dish, and trim excess edges.

Roll remaining dough to 1/8 inch thick. Cut into strips approximately 1/8 inch wide for the fishtail braid design.

Pinch five strips together and braid them by alternating crossing the outermost strips over the center.

Pour filling into the crust, fold edges over to create a border, and ensure a neat finish for supporting the braid.

Arrange braided strips around the pie's perimeter and brush with egg wash for a golden sheen.

Preheat oven to 375°F and bake for 45 minutes, then move to the bottom rack for an additional 10-15 minutes.