Prepare the dough for the crust: stir the flour, sugar, salt, baking powder and spices together in a large bowl. Using 2 knives or a pastry blender cut in the butter until the mixture resembles coarse crumbs. Stir in the egg until well moistened. Stir in the ice water until dough forms. Wrap in plastic wrap and chill for about 1 hour.
Preheat the oven to 375 degrees.
Stir the ingredients for the nut mixture in a small bowl, and set aside. In a large bowl (or food processor bowl), beat together all the ingredients for the filling until well blended and set aside.
Roll the dough out on a floured surface to form a 12-inch circle, and use it to line a 10 inch fluted removable bottom tart pan. Trim the edges of the dough with a sharp knife. Spread the nut mixture evenly over the bottom, and then pour in the sweet potato mixture. Decorate with the pecan halves. Bake for about 1 hour, until the filling is well risen and set. Transfer to a wire rack to cool. Serve with praline pecan sauce and whipped cream.
Melt the butter in a medium-sized heavy saucepan. Add the sugar and cook over low heat, stirring, until the sugar has dissolved and browned. Stir in the cream and pecans and cook over medium-low heat for 30 minutes, stirring often. Cool slightly before serving. It's a delicious way to top-off B.'s sweet potato pie Yield: about 1 1/4 cups;
From B. Smith's Entertaining and Cooking for Friends", Artisan 1995. .