Preheat oven to 200°C.
Place 1 potato on a board and make thin, evenly spaced cuts at 5mm intervals, about two-thirds of the way through.
Repeat with remaining potatoes.
Add oil, garlic, rosemary then season with a small pinch of sea salt and pepper and toss to combine.
Use a pastry brush to brush in between the hasselback cuts for maximum flavour.
Place in a roasting pan.
Bake in oven, basting with the garlic oil occasionally, for 1 hour or until golden brown and crisp.
Transfer to a serving bowl to serve.
