Peel the potatoes and cut them into rough shapes about as large as a ping-pong ball.

Heat the oven to 200°C/400°F.

Cook the potatoes in a pot of boiling water with the salt in it for 5 - 7 minutes. The potato chunks should be still firm, but soft enough that a fork can start to be pushed into them.

Drain the potatoes and add them to a large boil containing the oil.

Stir the potatoes well so that they are all coated with the oil. Small bits of potato may break off.  This is what makes them crispy.

Scrape the sprigs of rosemary with a sharp knife to release the oil inside, then add the sprigs to the potatoes.

Pour out the potatoes onto a baking tray with low sides, or a into a baking dish, and spread them out into a single layer.

Bake for 35 -45 minutes until they are brown and crispy.

Serve immediately.