In a large bowl, combine cold mashed potatoes, beaten egg, breadcrumbs, parsley, garlic powder, onion powder, salt, and pepper. Mix until well combined, ensuring the mixture holds together when pressed.

Divide the mixture into equal portions and shape each into a patty about half an inch thick. If the mixture is too soft, add more breadcrumbs until it firms up.

Warm 1 tablespoon of olive oil in a large skillet over medium heat. When the oil begins to shimmer, carefully place the patties in the skillet, ensuring they are spaced apart to prevent sticking. Cook for 4-5 minutes on each side until golden brown and crisp.

Heat olive oil in a skillet over medium heat. Place the patties in the skillet and cook for 4-5 minutes on each side. They should turn golden brown and develop a crispy texture. Listen for a gentle sizzle, which indicates the oil is at the right temperature for cooking.

Gently turn the patties over with a spatula, taking care to keep them intact. A fish spatula is ideal for this, as it provides the necessary support. Cook for an additional 3-4 minutes until the second side is golden brown and crisp, listening for a gentle sizzle.

After cooking, place the patties on a plate lined with paper towels to absorb any excess oil. This ensures they remain crisp. Allow them to rest for a minute or two before serving, so they retain their texture and are not too hot to handle.

Continue cooking the remaining patties in the skillet, ensuring they are evenly spaced. Add more olive oil if the skillet appears dry. Maintain medium heat to keep a steady sizzle, flipping the patties once they are golden brown on each side, about 3-4 minutes per side.

Once the patties are golden brown and crisp on both sides, transfer them to a serving plate. Serve immediately while warm, optionally garnished with chopped fresh parsley. For a bright, tangy finish, squeeze a little lemon juice over the top just before serving to enhance the flavors.

For extra flavor, serve with a side of sour cream or a dipping sauce of your choice. This complements the patties' crispy texture.

Transfer any remaining patties to a shallow, airtight container and place them in the refrigerator within two hours of cooking to ensure safety. When ready to enjoy again, reheat the patties thoroughly in a skillet over medium heat until they reach an internal temperature of 165 F (74 C).