Wash, peel and coarsely dice the potatoes and cook them in salted water for approx. 20 min. Drain the potatoes and mash or press them through a press and then leave them to cool. Add the cornflour, oil and salt, knead the dough well. Form thumb-thick rolls from the dough and cut into finger-thick slices. Press grooves into it using a fork. Add the gnocchi to boiling salted water and 1 tbsp oil. Cook the gnocchi for approx. 5 minutes, then scoop it out with a ladle.