In a large bowl, combine 4 cups mashed potatoes, 2 cups shredded mozzarella cheese, 1 large egg, 1/4 cup flour, and 2 tbsp. tablespoons of chopped young onions. Use a blender to knead the mixture until full. If the potatoes are too loose, add a tablespoon of flour.
Place a tablespoon of the potato mixture between your palms and form a 1 cm thick round patty. Dip both sides of the patty in breadcrumbs and place on a cutting board. Make cutlets with the rest of the mixture.
Heat oil in a skillet and fry the potato pancakes on both sides for 2-3 minutes or until golden brown.