Peel the potatoes and cut into 2.5 cm/lin pieces. Place them in a bowl, cover with cold water and leave to soak for 10—15 minutes. Drain, rinse and drain again, then dry thoroughly in a tea towel.

In a preferably non-stick large heavy frying pan or wok, heat about 60 ml/4 tbsp of the oil, dripping or butter over a medium-high heat, until very hot, but not smoking.

Add the potatoes and cook for 2 minutes without stirring so that they seal completely and brown on one side.

Shake the pan and toss the potatoes to brown on another side and continue to stir and shake the pan until potatoes are evenly browned on all sides. Season with salt and pepper.

Add a little more oil, dripping or butter and continue cooking the potatoes over a medium-low to low heat for 20—25 minutes until tender when pierced with a knife, stirring and shaking the pan frequently. About 5 minutes before the end of cooking, sprinkle the potatoes with the chopped rosemary.