Cook the potatoes in a large pan of boiling salted water for 15-20 mins until tender when pierced – they should slide off the knife when lifted. Drain and spread out on a tray to cool, about 20 mins. These can be cooked ahead and kept in the fridge until you’re ready to use them. Will keep chilled for up to a day.

Cut the potatoes into roughly 2cm cubes. Heat the oil in a large frying pan over a medium-high heat and cook in a single layer for 8 mins, undisturbed, or until a golden crust forms. Once they come away from the pan when given a nudge with a spatula, turn and cook for a further 8-10 mins, tossing or flipping a few at a time until golden all over.

Add the rosemary and cook for a further 5 mins. Season well with sea salt and serve.