In the work bowl of a food processor, pulse flour, pecans, salt, and sugar until combined. Add butter; pulse until mixture resembles coarse crumbs. Add 6 tablespoons ice water, 1 tablespoon at a time, pulsing until a dough forms.
Turn out dough onto a lightly floured surface, and shape into a disk. Wrap tightly in plastic wrap, and refrigerate until firm, at least 30 minutes.
Preheat oven to 350°.
On a lightly floured surface, roll dough into a 17½x12½-inch rectangle. Transfer to a 15½x10½-inch jelly roll pan, pressing into bottom and up sides. Fold edges under, and crimp as desired. Top with a piece of parchment paper, letting ends extend over edges of pan. Refrigerate for 10 minutes.
For filling:
Sprinkle pecans into bottom of prepared crust.
In a large bowl, whisk eggs until foamy. Whisk in sugar, corn syrup, melted butter, cane syrup, flour, salt, and vanilla until well combined. Pour egg mixture over pecans.
Bake until crust is golden brown and filling is set and puffs in center, 50 minutes to 1 hour, loosely covering with foil to prevent excess browning, if necessary. Let cool completely on a wire rack.
For glaze:
In a medium microwave-safe bowl, heat chocolate and butter on medium for 1 minute; stir until smooth. (If chocolate is not melted, heat for 30 seconds.) Spread on top of pie, leaving a 1-inch border. Let stand until chocolate is set.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/pecan-slab-pie-2/