1Slice the onions and sauté them in a pan over high heat with oil and salt.
2When softened, add a glass of water and cane sugar.
3Cut the potatoes into very small cubes and sauté them in a pan with two glasses of water, if the water dries out add another glass, until they are soft.
4At this point season with oil, salt, pepper, paprika if you like and also garlic powder if you like, add half of the Parmesan cheese.
5Roll out the pastry and prick it with a fork.
6Add the caramelized onions on the base, the cheese, the potatoes.
7Close the edges of the puff pastry and brush them with the yolk.