Sift 2 cups of all-purpose flour and 1/2 teaspoon of salt into a mixing bowl. Cut in 1/2 cup of vegetable shortening using a pastry cutter until the mixture resembles coarse crumbs. Gradually add ice water, one tablespoon at a time, mixing until the dough holds together. Shape it into a disc, cover with plastic wrap, and refrigerate for at least 30 minutes before rolling out.

Once chilled, take the dough out and place it on a floured surface. Roll out the dough evenly using a rolling pin until it's about 1/8 inch thick, ensuring it’s large enough to fit into a 9-inch pie pan. Carefully transfer the rolled-out dough to the pan, pressing it gently into the corners. Trim the edges and refrigerate the crust while you prepare the filling.

Peel and chop 2 cups of Louisiana yams into chunks. Place them in a large pot, cover with water, and bring to a boil. Cook for 30 minutes or until the sweet potatoes are tender when pierced with a fork. Drain the water, allow the sweet potatoes to cool slightly, then peel and mash them in a mixing bowl until smooth.

Preheat your oven to 400°F (200°C). While the oven heats, brush the pie crust with 2 tablespoons of melted butter and sprinkle 1/4 cup of light brown sugar evenly over the surface. Place the crust in the preheated oven and bake for 15 minutes, or until it's lightly golden. Remove it from the oven and set aside to cool while you prepare the filling.

In your mixing bowl with the mashed sweet potatoes, add 1/4 cup of melted butter, 1/2 cup of light brown sugar, 1/4 cup of granulated sugar, 2 large eggs, 1 cup of half-and-half, 1 teaspoon of ground cinnamon, and 1/4 teaspoon of ground nutmeg. Use a hand mixer or whisk to blend the ingredients together until the mixture is smooth and creamy.

Carefully pour the sweet potato mixture into the pre-baked pie crust, smoothing the top with a spatula. Reduce the oven temperature to 350°F (175°C) and bake the pie for about 1½ hours. You'll know it's done when the filling is set and a toothpick inserted in the center comes out clean.

After baking, remove the pie from the oven and let it cool completely on a wire rack, which may take about two hours. Once cooled, cover and refrigerate the pie for at least four hours or overnight for the best flavor. Serve slices chilled or at room temperature, ideally topped with whipped cream.