French fries

A potato is peeled, cut into planks, the planks cut into sticks, the sticks cooked in either water or in oil, then cooled to at least room temperature. At this point, the potatoes can be frozen and reserved until the next geologic age, or possibly a month or two. Finally, the cooled potato sticks are fried in hot oil, the so-called dehydration fry, to impart crispiness to the outside surface while maintaining a soft and fluffy interior. If the cook decides to fry the potatoes all at once, then too bad, limp soggy French fries for you! 

Fresh out of the hot oil, the fries are salted and otherwise seasoned to one's own preference.

French fries

The temperature of heated oil falls dramatically when a handful of cooled potatoes is dropped into it, so the oil is heated to excess of target cooking temperature in anticipation of decline.  The oil is heated to 360℉/182℃,  ten degrees above the target cooking temperature of 350℉/177℃.  If the oil temperature drops too much then the potatoes will absorb oil, we do not want that. We want the potatoes to repel the oil throughout the cooking process and that is done by keeping the oil hot. The cook must avoid the temptation of overloading the oil. A pot larger than necessary to boil potatoes in water is used to deep fry potatoes in oil because the fierce piling up of oil bubbles presents an unacceptable risk of overflow onto the flame or hot stove element. The same danger is present with cookers designed specifically for deep-frying. Always fill the pot with oil only half way, or even less is better, but less oil means increased temperature drop so fry in batches if necessary. For their own safety, get the kids out of the kitchen.

So, there ya go ↑, a 55° drop in Fahrenheit terms with just one potato. Maybe I should have started at an even higher temperature.

With the stove kept on high, the temperature quickly comes back up ↓ to 350℉/177℃, but I would have preferred it not drop as much as it did.

Look at 'em there ↓ so hot, exhausted from their workout, vulnerable to the application of salt, garlic powder, any number of curry powders, the full range of other spices, even finely grated hard cheese if I cared to.