Preheat the oven to 190ºC/375ºF/gas 5. Add the potatoes to a medium pan of boiling salted water, reduce the heat to medium and simmer for 10 to 15 minutes, or until cooked through. Drain and leave to steam dry, then place in medium roasting tray and mash lightly with a potato masher.
Throw in the garlic and rosemary, season with salt and pepper and drizzle with a good lug of olive oil. Place in the hot oven for around 40 minutes, or until crispy and golden. Delicious served with Spring lamb and asparagus.