Wash the potato very well and grate it into coarse strips into a bowl with cold water which will help remove the starch.
Drain off the starchy water from the potatoes completely.
To the same bowl add the water, flour, oil, grated Parmesan cheese, salt, pepper and rosemary.
Mix well with a wooden spoon until well incorporated.
Take a 25cm cast iron pan (or an oven safe dish) and rub with some olive oil to prevent the mix from sticking later.
Transfer the prepared mix and spread evenly.
Top with a drizzle of olive oil and some extra grated Parmesan.
Bake in a pre-heated oven at 180C for around 40-45 minutes until golden brown on top.
Remove from the baking pan, slice and enjoy!
