In a heavy medium saucepan, melt chocolate and butter over low heat, stirring frequently. Remove from heat; cool. Meanwhile, line a 9-inch pie plate with pastry. Trim; crimp edge.
In a bowl, beat eggs, sugar, syrup, and whiskey until smooth. Slowly stir egg mixture into chocolate. Stir in pecans.
Pour the chocolate-pecan mixture into pastry shell. To prevent over-browning, cover edge of the pie with foil. Bake in a 350 degree F oven for 25 minutes. Remove foil. Bake for 20 to 25 minutes more or until a knife inserted near the center comes out clean.
Cool on wire rack. Chill within 2 hours. Cover for longer storage.
If you like, pipe whipped cream on pie, sprinkle with shaved chocolate and garnish with chocolate pecan halves. Makes 8 to 10 servings.