Whisk together flour, sugar, and salt. Add cold butter and mix with a pastry blender or fork until mixture resembles coarse meal and the pieces of butter are pea-sized.

Add 1 tablespoon cold water and continue mixing. Continue adding water, 1 tablespoon at a time, and mix until dough holds together when you pinch it. (You may not need to use all of the water.)

Divide dough into 2 equal portions. Wrap dough tightly in plastic wrap and refrigerate for at least 2 hours.

Remove dough from refrigerator. If necessary, let it sit at room temperature for 10-15 minutes until slightly softened but still cold.

Flour work surface. Roll out dough into a circle about ¼-inch thick. Press into a 9-inch pie pan. Trim off the excess.

Preheat oven to 350°.

Place chocolate and butter in a microwave-safe bowl. Heat at half power in 30-second increments until chocolate melts when stirred and butter is melted. Stir until smooth. Set aside.

Lightly beat eggs in a large mixing bowl. Add corn syrup, sugar, vanilla, and salt. Mix well. Stir in chocolate/butter mixture until smooth. Stir in hazelnuts. Pour filling into crust.

Bake for 50-60 minutes or until filling is set.