* Wash the potatoes, place them in a large stock pot filled with water, and bring to a boil.
* Cook until the potatoes are soft without overcooking, to prevent them from breaking. Cooking time may vary depending on the size of the potatoes.
* Peel immediately and mash them on a large dish using a potato ricer or a food mill.
* Place in a skillet 3 tablespoons olive oil, the (optional) bacon and the onion. Sauté until the onion is soft and translucent.
* Add the mashed potatoes.
* Stir until the potatoes are fully combined with the onion.
* Using the back of the spoon even the edges and flatten the potatoes.
* Eventually use the back of a skimmer to flatten the surface and make it resemble a frittata.
* Lift the edge to check when the bottom is cooked and light golden. Place on the pan a dish slightly larger than the pan.
* Rotate the pan and the dish together so that now the potatoes are upside down on the dish.
* Add 2 tablespoons of olive oil to the skillet then slide the potatoes back into the pan so that the uncooked face is now on the pan.
* Use the back of a spoon make the surface and the edges smooth and even.
* The potatoes are ready when the bottom surface is lightly golden. Serve warm.