For the crust (enough for one 9-inch pie):
2 cups all-purpose unbleached flour
1/2 tsp salt
1/4 cup very cold unsalted butter or margarine
1/4 cup very cold vegetable shortening
1/3 cup ice water
For the filling (enough for 2 pies):
6 large sweet potatoes
3 large eggs
1/3 lb margarine or butter
2 Tbsp baking powder
1 tsp ground ginger
2 tsp ground cinnamon
1/2 tsp ground nutmeg
1/2 cup light brown sugar
1/2 cup honey
1/2 can condensed milk
To make the crust: In a large bowl combine flour and salt. Using a pastry blender or two knives, cut in butter and vegetable shortening. Add ice water and stir just until the mixture comes together. Work the dough as little as possible. The larger the pieces of shortening and butter that remain, the flakier the crust will be. Wrap the dough in plastic wrap and refrigerate for at least 30 minutes or until firm. (Chilling not only lets the dough relax; it also firms up the fat.)
To make the filling: Place sweet potatoes in a pot with water to cover, and boil until soft. Drain, and remove skin from potatoes. In a large bowl, mash potatoes well with a potato masher. Add baking powder, ginger, cinnamon, nutmeg, brown sugar, honey and condensed milk, and whip together until smooth.
Partially bake the pie crust: Press the crust into a 9-inch pie plate, and decorate or crimp the edges. There are several ways to keep the crust from shrinking or rising up while it bakes (called "blind baking"): either line the crust with aluminum foil, and fill with rice or dry beans; or line with foil, and invert the pie crust over another pie plate of the same size (the crust bakes as a “sandwich” between the two pie plates). Bake in a 425°F preheated oven for 10 minutes, or until the crust is a light golden color.
Raise oven heat to 450°F. Pour sweet potato mixture into the pie shells, and bake for 45 minutes or until pies are firm (because some ovens are “hotter” than others, check the pies after 45 minutes -- it could take a total of an hour for the pies to cook).