Two deep pots are heated, one with boiling water the second for shallow oil.
The water goes to 202℉, boiling point in Denver
The oil goes to 350℉
The potato is blanched in water, that is not fully cooked. Removed to a towel to dry completely, then dropped into the oil to finish.
Or, you can blanch the potato in 250℉ oil. Remove the potato and crank up the heat to 350℉ to dehydrate, until the bubbles nearly stop. If the cut potato is removed before the bubbles stop then the internal moisture will soften the crisp outer surface and the result will be soggy French Fries.
I noticed Paula Dean showed her double fry method is actually a triple fry method. She dropped them into the oil a third time immediately before serving.