Wash the potatoes and pop them in a large saucepan.
Add ½ teaspoon salt and enough water to just cover.
Bring to a boil. Cover and reduce heat.
Simmer for 15 to 20 minutes, or until tender when tested with a skewer.
Drain and return to the saucepan.
Place over medium heat for 2 minutes to dry the potatoes.
While the potatoes are cooking, preheat the oven to 200°C.
Pour the oil into a roasting pan and place in the oven for 2 minutes, or until really hot.
Squash the potatoes gently with a potato masher so that the skins burst.
Remove the roasting pan from the oven and add the potatoes and garlic cloves. Toss to coat completely in the oil.
Roast for 45 minutes, or until crispy, flipping them after 20 to 25 minutes.
Remove the potatoes and garlic from the pan, drain off the excess oil.
Pop the garlic from its skin, season with sea salt and cracked pepper, and serve sprinkled with lemon zest.