cut potatoes into 1 inch cubes and place in a pot of cold salted water. bring to a boil and cook for about 10 minutes, or until a skewer goes through it smoothly.
drain the potatoes completely and place them in the pot again to evaporate some of the moisture. just be careful so that they don't stick and burn the the bottom of the pot.
mash the potatoes until it is very smooth, leaving no chunks behind. season it with salt, pepper, and sugar.
add the cornstarch and mix throughly until it it dough-like, but still a little bit sticky. if needed, you can use more cornstarch. shape the mixture into 2 tablespoons balls.
flatten the balls gently and place ½ tbsp of mozzarella cheese inside. wrap the edges around the cheese, form a ball and flatten it again. repeat this with the rest of the balls.
add oil to a pan on medium heat. when the pan is hot, add the pancakes and fry for about 3 minutes on each side, or until golden brown.
serve immediately and garnish with parsley, along with your sauce(s) of choice. enjoy!