Combine brown sugar, flour, and pecans in a small mixing bowl; stir well. Add 3 tablespoons syrup and 3 tablespoons butter, mixing until well blended. Set aside.
Combine sugar, cornstarch, cinnamon, salt, and remaining syrup and butter; stir well. Pour syrup mixture over apple slices
Roll remaining pastry to 1/8- inch thickness, and place over filling. Trim edges; seal and flute. Cut slits in top crust to allow steam to escape. Bake at 425° for 25 minutes; remove from oven, and crumble reserved brown sugar mixture over top crust. Reduce heat to 350°, and bake an additional 10 minutes or until topping melts. Cool 10 minutes.