Heat the oil in a deep pan and test one chip first to see if the temperature is correct. The chips should fry slowly, so make sure the oil is not too hot. Fry in batches turning after a minute or two. Test for crispness by removing it from the pan and testing the middle. If it is still soft continue to fry until crispy. If the oil is too hot they will burn, so rather take a little extra time with lower temperature oil. They should take 3-4 minutes to cook crisp.