Deep fat frying is one of the trickier and more hazardous cooking methods. If you're not experienced in the technique, consult a reputable cook book, such as The Joy of Cooking, for safety precautions before deep fat frying.
2 small organic russet potatoes per person
Enough vegetable oil to fill the skillet 1/2 full
Scrub, then boil, potatoes until tender. Let them cool completely. Cut into wedges lengthwise, about 8 per potato, trying to keep them all close to the same size for even cooking. Heat oil in cast iron skillet to 365 degrees on a deep fat or candy thermometer. Slip the potatoes into the hot fat very carefully. Do not overcrowd the skillet.
When the furious bubbling dies down, check potatoes for browning. Remove from the skillet just before they're brown enough for you, as they will cook a little more while standing. Drain on paper towels. Salt. Eat immediately.
If you're cooking a second batch, be sure to let the oil come back up to 365 degrees. Oil can be cooled completely, strained through a coffee filter and saved for reuse.