Add the shredded potatoes to a bowl of water, stir to combine. Pour the potatoes over a wire mesh strainer and allow to drain.
Whisk the egg and egg white in a large glass mixing bowl until just incorporated, about 30 seconds. Sift the flour, granulated garlic, cayenne and cinnamon into the egg. Add the chives. Sprinkle with 3 teaspoons each salt and black pepper; whisk until smooth. Fold in the sweet potato and potato, making sure the batter is thoroughly combined.
Set a large cast-iron or heavy-bottomed skillet over medium heat. Add the oil. Working in small batches, drop about 3 tablespoons per latke into the skillet just before the oil begins to smoke. Flatten each slightly with a slotted metal spatula. Make sure to not overcrowd the skillet.
Crisp the latkes until the bottoms are caramelized, 2 to 3 minutes. Flip with the spatula and continue crisping the second side for about 6 minutes total. The latkes should be cooked through and a dark, golden brown. Transfer to a paper-towel-lined dish. Season lightly with salt and pepper. Serve immediately, garnishing each latke center with a small dollop of sour cream and a sprinkle of torn parsley leaves.