1: Peel the potatoes and rinse them. If you want to make "old-fashioned" crisps, do not peel them, just scrub them thoroughly under running water.
2: Slice the potatoes thinly and evenly. I advise you to use a mandolin, more-or-less essential for producing even slices.
3: The ideal thickness you should aim for is 1 mm.
4: Rinse the slices in a bowl of water.
5: Drain and dry thoroughly on a tea towel.
6: When dry, lower into very hot frying oil. Do not put in too many at a time, as they will create a white foam that can froth up and overflow. Fry until the froth disappears (around 3 minutes).
7: Remove the crisps from the oil and leave for 5 minutes.
8: Put the chips back into the oil and fry again until golden brown.
9: Tip onto absorbant paper, and sprinkle with salt. Eat immediately.
10: For flavoured crisps, replace the salt with a mixture of a little salt and your choice of spice (curry, paprika, etc.).
Remarks
The variety of potato affects the crisps' quality. I find I get the best results with Bintje.