Scrub the sweet potatoes clean under running water. Remove the skins using a vegetable peeler if desired.
Place the sweet potatoes on a large cutting board. Using a paring knife or small chef’s knife, cut into matchsticks about ½-inch thick and several inches long.
Bring a large pot of water to a boil. Add the cut sweet potatoes to parboil for about 5 minutes until slightly soft but still firm.
Remove the sweet potatoes from the boiling water using a slotted spoon or skimmer. Place on the cutting board to cool for a minute. Then pat dry using paper towels to remove excess moisture.
Preheat 2 inches of oil to 350°F in a deep fryer or medium saucepan. Set aside a wire cooling rack.
In a medium bowl, whisk together the cornstarch and water. Adjust the ratio as needed to reach a thin pancake batter consistency.
Use kitchen tongs to dip a half-dozen fries in the cornstarch mixture, shaking off the excess. Then drop the fries gently into the hot oil one at a time, frying for 1 to 2 minutes or until golden brown.
Remove the fries to the wire rack and allow to cool for several minutes. In the meantime, continue battering and frying the remaining sweet potatoes in batches until finished.
Season the fries with salt, pepper and paprika and serve warm with your favorite aioli or dipping sauce.