Using a deep-fry thermometer to register the temperature, heat enough oil to 350 degrees F in a large heavy-bottomed pot to 1/3 full. Line a baking tray with paper towels. Put the cornstarch in a bowl. In batches, coat the tofu with cornstarch and gently put in the hot oil, separating the tofu fries as they are cooking to prevent sticking. Remove the tofu fries from the oil once golden brown, season with salt and repeat with the remaining tofu fries.