Place 1 cup of flour, salt and sugar into a food processor and pulse until combined. Add the butter and shortening, and process until the dough just starts to collect in uneven clumps (it should look like cottage cheese)
Scrape the bowl with a spatula to push it back down towards the blade. Add remaining flour and pulse 4 to 6 times until the mixture is evenly distributed. Empty the mixture into a medium sized bowl.
Sprinkle vodka and water over the mixture. With a rubber spatula, use a folding motion to mix pressing down on the dough until it is slightly tacky and sticks together. Form the dough into a ball and flatten into a 4 inch disk. Wrap in plastic wrap and refrigerate at least 45 minutes before forming into pie crust.
Preheat the oven to 450 degrees Fahrenheit with the rack in the middle position.
Lightly clean the sweet potatoes under running water. Using a fork, prick the sweet potatoes about 6 to 8 times each, about ΒΌ inch deep.
Place the sweet potatoes directly on the middle rack, and then place the baking sheet covered in foil just below to catch the drippings.
Bake for 50 to 65 minutes. Once the sweet potatoes start dripping from the pierced holes, that's the sign to start checking for their doneness. They will be done when they yield to a gentle squeeze.
When done, remove from oven and squeeze and break open with tongs to let the steam and heat out.