Put the potatoes in a large sauce pan with boiling water. Simmer for 10 minutes, or until they are tender when you put a fork/knife in them. Drain and leave to sit in a colander for 5 minutes, to allow the moisture to evaporate.
Put them on a large baking tray. Drizzle with olive oil and add the garlic, salt and pepper and mix well.
Using a fork (or glass or potato masher), gently but firmly smash them down.
Put them in a preheated oven at 200°C/400°F/Gas 6 for 30-35 minutes, until the edges are perfectly crispy.
Don't over boil the potatoes. You want them to be tender when you put a knife/fork in it, but not falling apart.
You definitely don't need to smash these neatly. The messier they are, the more edges to get crispy.
Don't skip the step of leaving them in the colander after you have drained them. This allows them to get rid of some of the extra moisture to help with the crispiness.
Make sure that the potatoes have lots of room on the baking tray. If the tray is too full and the potatoes are too close together, then they will steam rather than roast. If you don't have a tray big enough for all the potatoes, then use two trays.
For extra flavour, you can drizzle these with butter before they go in the oven.
The nutritional information for this recipe won't be accurate, and will be an overestimate. This is because they don't absorb all of the oil that has been added to the pan.
Make these even more indulgent by sprinkling over some chopped grilled bacon before serving. This is a great option if you are adding the Parmesan too.