Fill a large saucepan with water and bring to a boil over a high heat. Scrub each of the potatoes until they're clean and use a sharp knife to cut them into quarters.
Add the potatoes into the boiling water and turn the heat down slightly. Leave the potatoes to cook uncovered for 15-20 minutes, until they're soft enough for you to easily insert a knife into the center. While the potatoes are cooking, preheat the oven to 400F / 200C .
When the potatoes are cooked, drain off the water and turn off the heat. Return the pan to the stove for a final 30 seconds, shaking the pan constantly so the outsides of the potatoes dry and fluff up. This is what will help them absorb all the delicious flavor when roasting.
Tip the potatoes into a large-oven proof dish and drizzle with the olive oil. Sprinkle over the rosemary, garlic powder, onion powder and salt. Use your hands to turn the potatoes over, making sure they're all evenly coated with the oil and seasonings.
Nestle the whole garlic cloves in between the potatoes and bake in the oven for 30-40 minutes until golden brown and crisp.