Fill a one cup measuring cup about halfway up with ice, then add water and 2 tbsp apple cider vinegar.
Roasting sweet potatoes
Preheat oven to 425°F. Scrub the sweet potatoes and wrap them in aluminum foil. Poke a few holes through the foil and into the sweet potatoes with a fork and transfer them to a baking sheet. Place the baking sheet in the oven and bake for 40 to 60 minutes, or until you can smoosh the foil package with your oven mitt. Remove from the oven and place on a wire rack. When it cool enough to touch, carefully remove the skin from the sweet potatoes. Transfer the sweet potato flesh to a food processor or blender and puree until smooth. Set aside. You can store the sweet potato puree in an airtight container in the fridge.
Blind baking the crust
Put flour, sugar and salt in a bowl and mix well. To this add in butter and combine until mixture resembles breadcrumbs. Then pour in water-vinegar mixture till a dough starts to form. Then transfer to plastic wrap and spread it into a disc. Wrap in plastic and refrigerate for at least 2 hours or ideally, overnight. The dough will keep in the fridge for a few days or in the freezer (double wrap it in plastic wrap for up to a year).
Preheat oven to 450°F.
Place the prepared pie crust from freezer with the rack on the lowest level. Fill the crust with the dried beans (they should come all the way up to the crimps) and place the pie pan on a baking sheet. Transfer the baking sheet to the oven and bake for 25 to 27 minutes. Check for doneness by peeling up a piece of foil—the crimps should be light golden brown. Remove the baking sheet from the oven and transfer to a cooling rack. After 6 minutes, carefully remove the foil and beans. Pie crust is ready for filling.
In a bowl, combine the sweet potato puree with the butter, brown sugar, cardamom, cinnamon, ground ginger, nutmeg salt, cornmeal, evaporated milk, cream, and eggs and combine until it well blended.
Place the blind-baked shell on the parchment-lined baking sheet.
Pour the sweet potato filling into the pie shell until it reaches the bottom of the crimps. Transfer the baking sheet with the pie on it to the oven and bake for 40 to 50 minutes, until the edges are puffed and the center jiggles only slightly when shaken.
Remove the baking sheet from the oven and transfer the pie to a wire rack. Let cool for 15 minutes, then decorate with precut shapes. Allow the pie to fully cool for another 4 to 6 hours. When the pie is at room temperature, slice it into 6 to 8 pieces and serve.
Store leftover pie, well wrapped in plastic wrap, in the refrigerator for up to 2 days.