To cook pierogi, bring a large pot of salted water to a boil. Carefully add the pierogi, ensuring they are not overcrowded, and cook for about 5 - 6 minutes or until they float to the surface. Once cooked, remove them with a slotted spoon and let them drain. For frying, heat a skillet over medium heat, place boiled pierogi and add a couple of tablespoons of oil or butter. Fry on each side until they are golden brown and crispy. Serve hot, optionally topped with caramelized onions, sour cream, fresh herbs or favorite sauce to enhance their flavor.