Peel and cut potatoes lengthwise. Try to cut them into somewhat uniformly sized sticks to facilitate even frying.
Place the cut potatoes into a large bowl and top with water and a splash of vinegar (will prevent them from browning and make them crispier). Place in fridge for 30 minutes at least and up to 4 hours.
Once you take the potatoes out of the fridge and the water, pat dry them thoroughly.
In a deep pot (dutch oven works really well) heat the olive oil to about 375°F.
Fry in batches without overcrowding.
When you see them turn golden you may begin to remove them with a slotted spoon.
Place on paper napkins to absorb the excess oil.
Repeat the frying step once more for each batch, fry another 2-3 min, to get perfectly crisp fries.
Place on paper napkin again and lightly season with salt.
Serve in two heaps covered with grated feta cheese and oregano.