Preheat the oven to 400 degrees F. Lightly dust a work surface with the flour. Roll out the dough the size of a large pan and about 1/4-inch thick. Carefully fold the dough into fourths and place on the pan. Form the crust to fit the pan. Crimping the edges. In a mixing bowl, toss the sweet potatoes with salt and vegetable oil. Roast the sweet potatoes for 1 hour, or until the potatoes are tender. Remove from the oven and cool. Remove the skin from each potato. Place the potatoes in a mixing bowl and mash the potatoes until smooth. Stir in the eggs, cream, cane syrup, cinnamon and nutmeg. Spread the sweet potato mixture over the pie crust. Bake the bars for 25-30 minutes, or until the bars are set. Remove from the oven and cool.
Combine the flour and salt in a bowl. Add the lard and work it in with your hands until the mixture resembles coarse crumbs. Add the water, 1 tablespoon at a time, working it in with your hands. Add only as much as you need to make a smooth ball of dough. Wrap it in plastic wrap and refrigerate for at least 30 minutes. Remove the dough from the refrigerator and place it on a lightly floured surface. Roll the dough out on the floured surface. Gently fold the dough in half and then in half again so that you can lift it without tearing it, and unfold into a pan. Fill and proceed as directed in the recipe.