From Barefoot Contessa in Paris: Easy French Food You Can Make at Home by Ina Garten
2 large oval Idaho potatoes, peeled
Sea salt or kosher salt (Fleur de sel is best, but expensive)
Pour at least 1 inch of oil into a deep pot and heat to 350 degrees. A dutch oven is best because the potatoes, once you start to fry them, will cool the oil down and you have to wait between batches. Make sure you have enough oil--a large bottle might be enough.
Slice the potatoes into thin matchsticks (1/8 inch thick) with a vegetable slicer or mandoline. Drop into cold water.
Once all the potatoes are sliced, strain and dry them thoroughly with paper towels.
Drop the potatoes in batches into the hot oil and cook for 3 to 5 minutes, until golden brown.
Strain with a skimmer and drain on paper towels.
Sprinkle with salt and serve hot.
If you're cooking more than two potatoes worth, you can keep them hot in a 350 degree oven while you're finishing the batches.