In our experience, blanching ahead of the final fry produces a superior chip.
Blanching is simply frying the raw chips in hot fat to cook them through and seal them, but at a temperature which will not turn them brown. They can then be set aside, for up to two days in a refrigerated space, and given their final fry when they are about to be served. The result is a hot chip, crispy and golden on the outside, fluffy and white on the inside.
We blanch our varieties for 6 minutes at a temperature of 160 degrees Celsius and then set aside until needed.