For the dough: Place the softened butter, sugar and salt in the bowl of an electric mixer; beat on high speed until the mixture is creamy. Add the 1/2 egg and beat 30 seconds. Add the milk and beat on high speed 2 minutes. Add the flour and beat on medium speed 5 seconds, then on high speed just until blended, about 5 seconds more (overmixing will produce a tough dough). Remove the dough from the bowl and shape into a 5 inch patty about 1/2 inch thick. Lightly dust the patty with flour and wrap in plastic wrap; refrigerate at least 1 hour, preferably overnight. (The dough will last up to one week refrigerated.)

On a lightly floured surface roll out dough to a thickness of 1/8 to 1/4 inch. Very lightly flour the top of the dough and fold it into quarters. Carefully place dough in a greased and floured 8 inch round cake pan (1 1/2 inches deep) so that the corner of the folded dough is centered in the pan. Unfold the dough and arrange it to fit the sides and bottom of pan; press firmly in place. Trim edges. Refrigerate 15 minutes.

To assemble: Spoon the sweet-potato filling evenly into the dough-lined cake pan. Pour the pecan syrup on top. Bake in a 325 degree oven until a knife inserted in the center comes out clean, about 1 3/4 hours. (Note: The pecans will rise to the top of the pie during baking.)

Cool and serve with Chantilly Cream. Store pie at room temperature for the first 24 hours, then (in the unlikely event there is any left) refrigerate.