I heat the cast iron skillet to searing hot THEN add the oil, about 1/4" high, then the potatoes. Shortening fries potatoes so much better but not many like to use shortening. I don't peel the potatoes if I'm frying them. Turn the heat to med heat and let them alone until the steam from the frying gets thin. I turn up the heat to high and turn the potatoes and let the crisp. We like them crusty red. Smaller red potatoes have less starch in them then big potatoes so fry much better.