Cut half of the potatoes into large cubes, place them in a medium saucepan, salt generously and cover with cold water.
Bring to a boil and reduce the heat to low and simmer for 10 minutes.
Meanwhile, grate the remaining potatoes. Add a little salt to the grated and reserved.
When the boiled potatoes are ready, drain them, put them back in the pan, and add ¼ cup of milk and mash.
Put the grated potatoes in a clean dishcloth, and squeeze and twist the cloths to remove the liquid.
Add the grated potatoes to the mashed potatoes.
Place the egg, remaining milk, flour, Sardo Sliced Green Olives, salt and pepper to taste, mix well and add to the potatoes.
Heat a large non-stick frying pan over medium heat and add the butter.
Add ¼ cup of dough to the pan and spread a little.
Cook for about 4 to 5 minutes. Flip and cook for another 5 minutes.
Serve hot with green onions and sour cream!