Preheat oven to 230°C/450°F.
To a large pot add 3 liters of water, salt and baking soda and bring to a boil.
Peel and chop potatoes, then boil for 10-15 minutes until fork tender. Boiling the potatoes with baking soda helps breaking down the pectin, creating a rough surface and thus more crispiness.
Strain the potatoes, then shake to roughen the surface.
Infuse the oil with garlic and rosemary. Fry until the garlic just begins to turn golden, then strain and set garlic/rosemary mixture aside, so it doesn’t burn in the oven.
Add the potatoes to a baking sheet, drizzle with the infused oil, spread out evenly and bake for 50-60 minutes, turning them 2-3 times, every 20 minutes.
Transfer to a large bowl to add the garlic/rosemary mixture and a pinch of salt, then toss to coat.
