The shape of the cut potato is a highly personal preference. Some people like an irregular shape; to get it, insert a knife about ½ inch (1.5 cm) into a peeled potato and then rotate and lift the knife, breaking off an irregularly shaped piece. Rotate the potato slightly and repeat. Others prefer thin, round slices.
The choice of pan is key. It should be a 10-inch (25 cm) nonstick skillet, with its nonstick properties fully intact. In most Basque homes, there is one pan used always and sometimes exclusively for making tortilla.