Peel the potatoes and washed. Cut into slices of medium thickness. Fry in a highly preheated oil until softened slightly. Drained of fat and set aside to cool slightly. After cooling smash, but not pureed. Beat eggs, add salt to taste, add pepper, chopped onion. Mix, then add and potato, parsley, maize, ham and mushrooms. All the mixture is stirred well. Baked in a deep pan, preferably non-stick coating, to tip the cake using a large dish, such as to cover the pan to turn easily. After baking tin with butter and serve.