Half-fill a large pan with water. Add a large pinch of salt. Cover and put on a high heat to come to the boil. Preheat your oven to 190°C/Fan 170°C/Gas 5.

Scrub and peel the potatoes. Chop them into roughly equal-sized chunks, around 3-4cm across. Pop them in a large colander and rinse under cold water to get rid of some of the starch. When the water in the pan is boiling, add the potatoes. Bring back to a gentle simmer, and then simmer for 5 mins.

Drain the potatoes, then tip them back into the pan. Gently shake them to rough up the edges (this will help the potatoes crisp up in the oven). Lay a couple of clean tea towels out on your kitchen surface and tip the potatoes onto them. Spread the potatoes out and let them steam-dry for up to 10 mins (no longer than that or the potatoes will develop a ‘skin’ and become leathery).

Meanwhile, add 4 tbsp oil to a large roasting tin (or 2 medium tins). Put them in the oven to heat the oil for 10 mins.

Take the roasting tin out of the oven. Add the potatoes and season with a pinch of salt. Turn them a few times to coat in the hot oil. Make sure the potatoes aren’t too crowded in the tin – it’s better to use two tins and give the spuds room to roast, rather than cramming them in so they end up steaming.

Roast for 40 mins, turning the potatoes after 30 mins, till they’re golden brown. Meanwhile, pick the rosemary leaves off their woody sprigs.

After 40 mins, remove the tin from the oven. Scatter over the rosemary. Season with salt and pepper. Toss again to coat the potatoes in the herbs.

Return the potatoes to the oven for 10-15 mins till golden brown and crisp. Transfer to a dish and serve.