1. Preheat oven to 375 degrees F (190 degrees C). 2. Prepare dough for one 9 inch pie. Refrigerate until ready to bake. 3. Blend together the butter, sweet potatoes, eggs, brown sugar, ginger, cinnamon, nutmeg, vanilla, salt, corn syrup and evaporated milk. Pour filling into crust and sprinkle with chopped pecans. 4. Bake for 40 to 45 minutes, or until inserted knife comes out clean. Set aside to cool. 5. Beat together whipping cream, sugar and liqueur until soft peaks form. Top pie with whipped cream and pecan halves.