Wash the potato and cut into thin slices. If the potato is fresh, without sprouts, then the peel can also be consumed.
Heat a bit of olive oil in a pan and place the potato slices in a fan shape, working from the outside in. The potatoes should overlap a bit. Sprinkle the parmesan over the potatoes and cover the pan. Let simmer for 5 minutes.
Now pour the tomato sauce evenly over the potatoes, and add the oregano. Arrange the mushrooms and mozzarella in a circular pattern so that you leave a hole in the middle. Finally, crack an egg into the center of the potato pizza.
Cover the pan and let cook for 6 minutes, before carefully transferring to a plate. Place the ham on the pizza and season with fresh ground pepper.