Peel the potatoes and cut into spaghetti with a spiral cutter. Pat dry on paper towels, then deposit in a bowl.
Peel and chop the onion and garlic. Cut the leek into slices.
In a pan, fry the onion and garlic cubes in hot oil until translucent. Add the potatoes and a piece of butter and fry slowly over a low heat. Add the chili rings and the leek and turn everything over and over until the potatoes are browned. Finally, season to taste and cut the basil leaves into fine strips and sprinkle over the potatoes.
Arrange the potato spaghetti on a platter, garnish and serve.