Rinse and peel potatoes. Cut the potatoes in half length wise, then cut the halves in half and thinly slice.
Put the oil and butter in a large frying pan and heat until the butter is melted. Add the potatoes,onion, black pepper, salt and garlic powder. Mix everything together and lightly fry for 15 minutes or until the potatoes are light brown and the onion is crispy.
Pour in the water, cover and let simmer for 15 minutes. Sprinkle with parsley and serve.