Preheat the oven to moderate (~180°C). Wash and peel potatoes, cut in half lengthways. Place in a saucepan of boiling salted water, simmer for 10 minutes then drain. Dry the potatoes on absorbent paper and roughen up the surface with a fork to assist them to crisp nicely when cooking. Chop the vegetable shortening and place in a shallow pan then place in the oven until the shortening melts. Remove from the oven and add in the potatoes. Bake in the oven 45 minutes then drain off most of the vegetable shortening. Return to the oven and bake for a further 15 to 30 minutes, turning them occasionally, until golden brown.