Make the crust: Preheat the oven to 350 degrees F. Line a 9-by-13-inch baking dish with foil, leaving a 2-inch overhang on two sides; coat the foil with cooking spray. Pulse the pecans in a food processor until finely ground. Add the flour, granulated sugar and salt and pulse to combine. Add the cold butter and pulse until the dough starts clumping together (it will still be crumbly). Transfer to the baking dish and press into an even layer with your fingers. Bake until golden brown and set, 25 to 30 minutes.
Meanwhile, make the topping: Whisk the corn syrup, granulated sugar, brown sugar, eggs, melted butter, vanilla and salt in a large bowl until smooth, then stir in the pecans.
Spread the topping over the warm crust and sprinkle evenly with the chocolate. Return to the oven and bake until the top is set and no longer jiggly, 25 to 30 minutes. Transfer to a rack and let cool completely in the pan. Remove and cut into diamonds or squares.