Preheat oven to 200C/400F. Mix Parmesan Mixture in a bowl. Drizzle oil in 22 x 33cm / 9 x 13" glass baking dish (Note 2). Tilt pan to spread all over the base. Use a spoon to scatter the Parmesan Mixture over the base. Spread as evenly as you can. Once sprinkled, do not touch - don't try to spread it. Place potatoes cut side down, pressing firmly. Optional: drizzle top of potatoes with a touch of oil or spray with oil, then sprinkle with salt. Bake potatoes for 35 - 40 minutes or until they are soft and the parmesan crust is deep golden (you can check through the glass!) REST for 5 minutes. Then use an egg flip to cut between every 4 or so potatoes (i.e. cutting through the parmesan crust which bonds between each potato - see video), then scoop up 4 or so potatoes and flip them upside down so the cheese side is up on a serving platter. Serve with Dipping Sauce, if using, and sprinkle over extra green onions if desired. Serve as a side dish or as nibbles!