Deep-fried fries are cut potatoes that are cooked in hot oil, although they might first be parboiled in water. One of the main goals when making fries is for each one to individually have a crisp, slightly dry exterior with a moist, tender and fully cooked interior. When performed correctly, deep-frying can achieve these results very quickly, while cooking methods such as baking can potentially dry out the fries. Many restaurants regularly serve deep-fried fries and employ specially designed equipment to help avoid burning the potatoes while they are cooking, which can happen very quickly. Some deep-fried fries are coated in batter, flour or spices before they are cooked, either to provide a crisper texture or a different flavor.
One of the main goals when making deep-fried fries is to achieve a crisp outer crust on the potatoes, and there are two generally accepted methods of doing so. The first, which works well with waxy potatoes, involves cutting the potatoes and boiling them in water until they have softened and partially cooked on the inside. This allows the potatoes to be deep-fried quickly at a high temperature so the outside is crispy without the need to wait for the interior to fully cook from the heat of the oil alone.
A second method involves soaking the potatoes in water before cooking to remove a portion of their starch, which can cause them to burn or become gummy. Potatoes that are soaked are not usually boiled in water afterward and are instead deep-fried in two stages and at different temperatures to achieve the desired results. This method works well on potatoes that do not have a thick, waxy texture.
The temperature of the oil being used to make deep-fried fries is very important to the final dish. If the oil is too hot, then the fries will quickly brown or burn on the outside while the inside remains mostly raw. Oil that is too cool will soak into the potatoes instead of interacting with the inner moisture, creating a heavy and greasy fry that might have a bitter taste or be very undercooked.
When the potatoes are ready to be cooked, they are lowered into the oil and allowed to deep-fry for a few minutes. For parboiled potatoes, this process can go very quickly and requires constant attention. If the potatoes were only soaked in water, then the first deep-fry is done at a low temperature to allow the inside to steam until done. This is followed by a second period in hotter oil to form the crust. In either case, great care has to be taken, because the color of the deep-fried fries in the oil can be deceptive and they can easily burn despite appearing only golden brown in color.