Mash the boiled potatoes in a large bowl until smooth. Add salt, cornstarch, and any optional seasonings like black pepper, garlic powder, or Parmesan cheese. Mix well.
Take small portions of the mixture and shape them into cylindrical or round croquettes.
Dip each croquette into the beaten eggs, then roll in breadcrumbs until fully coated.
Heat oil in a deep pan over medium heat. Fry the croquettes in batches for about 2-3 minutes per side, or until golden brown and crispy.
Remove and drain on paper towels. Serve hot with your favorite dipping sauce.