Pre heat oven to 200C. Pour 4 tablespoons of olive oil onto a large baking tray and place in the oven to heat.
Fill a large saucepan with water and bring to the boil on the hob.
Peel and chop your potatoes (I usually cut my potatoes into 4 or 6 pieces depending on how big they are). Transfer the potatoes to the boiling water and par boil for around 10 minutes (until starting to soften, but not falling apart).
Drain the potatoes into a colander and shake to fluff up the outsides.
Carefully remove the tray from the oven and pour the potatoes into the hot oil (they should sizzle). Pour the remaining tablespoon of oil over the potatoes and top with salt, pepper and fresh rosemary.
Place back in the oven for around 1 hour to 1 hour and 15 minutes (ensuring to shake the potatoes every half an hour so they don't stick). Serve warm and fresh from the oven.
