Cream butter with 1/3 cup firmly packed dark brown sugar; Stir in pecans; press over bottom of pastry shell. Bake 10 minutes in a preheated 450 degree oven; cool on wire rack. Beat eggs slightly; Stir in pumpkin, 1/2 cup firmly packed dark brown sugar, the granulated sugar, salt and spice; Beat in scalded milk mixture. Pour into pie shell. Bake 50 minutes in a 350 degree oven until center is soft set. Serve just warm topped with whipped topping.