How to Make It
Prepare the Chocolate Crust: Pulse flour, sugar, cocoa, and salt in a food processor until combined, 3 or 4 times. Add cold butter, and pulse until mixture resembles small peas, 8 to 10 times. Add 4 tablespoons of the water, 1 at a time, and pulse just until moist clumps form and mixture begins to form a ball, 8 to 10 times. (If necessary, add up to 1 tablespoon more ice-cold water, and pulse until desired consistency is reached.) Gather dough into a ball, and flatten into a disk. Wrap in plastic wrap, and chill until firm, about 1 hour.
Preheat oven to 325°F. Roll dough into a 12-inch circle (about 1/8 inch thick) on a lightly floured surface. Fit into a 9-inch pie plate; fold edges under, and crimp.
Prepare the Filling: Sprinkle 1 cup of the chocolate chips evenly over bottom of piecrust. Whisk eggs in a large bowl until frothy. Add melted butter, and whisk until fully incorporated. Whisk in syrup, sugars, flour, vanilla, and salt. Stir in chopped toasted pecans. Pour mixture over chocolate chips in piecrust. Arrange pecan halves evenly over mixture.
Bake in preheated oven until set around edges and slightly wobbly in center, 55 minutes to 1 hour, tenting with aluminum foil after 35 to 40 minutes. Cool completely before slicing, about 3 hours.
Place remaining 1/3 cup chocolate chips in a microwavable bowl, and microwave on MEDIUM (50% power) until melted, 1 minute to 1 minute and 30 seconds, stirring every 30 seconds. Drizzle over pie.