Scrub and peel the potatoes. To cut them into perfect French fries, square them up by trimming of the top, bottom and four sides of the potato to start with a block. Then, slice the potatoes into approximate 1/3 inch (less than 1/2 centimeter) slabs, and then cut the slabs into approximate 1/3 inch strips.
Place the cut potatoes into a large bowl of cold water. Leave for 15 minutes. This removes excess starch from the potatoes that would cause them to stick together when cooked, and helps them be extra crispy.
While the potatoes are soaking, pour the oil into a deep pot, at least 5 inches deep. Begin to heat the oil on medium heat.
After 15 minutes, drain and thoroughly rinse the potatoes. Lay them out in a single layer on a clean kitchen towel. Dab them dry with another clean towel to remove all water from all sides of the cut potatoes.
Raise the heat under the pot to medium high. Bring the canola or peanut oil to 270°F (130°C) when measured with an instant-read thermometer.
First fry: Working in batches, place the dried cut potatoes into the hot oil. You may use a fry basket or mesh strainer to lower them into the oil, and to remove them from the oil. Blanch them for 8 minutes. They will look pale and flabby. That's OK! Lay them out on a baking sheet to cool, separating them with tongs.
Second fry: Raise the oil to 350°F (180°C.) Mind your temperature. When the oil is at temperature (use your instant-read thermometer again) place some of the blanched potatoes into the hot oil, being sure not to overcrowd them. You'll be doing this step in batches unless you're only cooking a few potatoes. Cook the potatoes until they are a nice medium-golden color, or to your liking.
Remove the potatoes with a strainer (or fry basket if you're using one) and put them into a large bowl.
Toss with a generous amount of your favorite salt, and serve while hot with excellent ketchup.