Wash the potatoes and cut them into batons. No need to peel them if the skin is thin.
Place them into a large pot of salted water and bring to the boil.
Boil for 8 minutes until they start to become slightly tender, but still holding their shape.
Drain and let steam for 10 minutes.
Preheat the oven to 430F / 220c.
Place the potatoes into a large bowl, and add the oil, garlic powder. onion salt, rosemary and pepper.
Gently combine the potatoes in the seasoning using your hands to ensure they are all well coated.
Place the fries onto a baking sheet in a single layer, without the fries touching.
Bake for 30 to 40 minutes until golden brown and cooked through.
Serve with grated grana padana.