1. Adjust oven rack to middle position and heat oven to 200°F. Set wire rack in rimmed baking sheet. Whisk cornstarch and 1/2 cup cold water together in large bowl.

2. Bring 2 quarts water, 1/4 cup salt, and baking soda to boil in Dutch oven. Add potatoes and return to boil. Reduce heat to simmer and cook until exteriors turn slightly mushy (centers will remain firm), 3 to 5 minutes. Whisk cornstarch slurry to recombine. Using wire skimmer or slotted spoon, transfer potatoes to bowl with slurry.

3. Using rubber spatula, fold potatoes with slurry until slurry turns light orange, thickens to paste, and clings to potatoes.

4. Heat oil in 12-inch nonstick skillet over high heat to 325°F. Using tongs, carefully add one third of potatoes to oil, making sure that potatoes arent touching one another. Fry until crispy and lightly browned, 7 to 10 minutes, using tongs to flip potatoes halfway through frying (adjust heat as necessary to maintain oil temperature between 280 and 300°F). Using wire skimmer or slotted spoon, transfer fries to prepared wire rack (fries that stick together can be separated with tongs or forks). Season with salt to taste and transfer to oven to keep warm. Return oil to 325°F and repeat in 2 more batches with remaining potatoes. Serve immediately.

Serves 4 to 6