Preheat your oven to 220°C (200°C fan) and place a large, sturdy baking tray inside to get hot.

Place the scrubbed potatoes in a large saucepan and cover with cold, salted water. Bring to the boil and cook for 15-20 minutes, or until the potatoes are completely tender when pierced with a knife.

Drain the potatoes carefully into a colander and leave them to steam-dry for at least 5-10 minutes. This step is vital for removing surface moisture, which helps them become incredibly crispy later. Give the colander a gentle shake to rough up the edges slightly.

Carefully remove the hot baking tray from the oven. Pour the olive oil onto the tray, then add the crushed garlic cloves and rosemary sprigs. Swirl them around in the oil for 30 seconds to start releasing their flavours.

Tip the steam-dried potatoes onto the hot oil and turn them gently to coat. Spread them out, ensuring there is plenty of space between each one.

Using the base of a glass or a potato masher, gently but firmly press down on each potato until it’s about 1.5-2cm thick. Don't worry if they break apart a little – those are the bits that will get extra crispy! I find that a flat-bottomed mug works best for an even press.

Sprinkle generously with coarse sea salt and freshly ground black pepper.

Roast for 25 minutes. Then, remove the tray from the oven, carefully flip each potato over, and return to the oven for another 20-25 minutes, or until they are deeply golden-brown, crisp, and sizzling.

Remove from the oven, discard the rosemary stems and garlic skins if you wish (the soft garlic is delicious squeezed out and eaten!), and serve immediately.