Begin by peeling and chopping 2-3 medium Yukon Gold potatoes into chunks. Place them in a pot of salted water and boil for about 15-20 minutes, or until fork-tender. Meanwhile, finely chop one medium onion and sauté it in a little oil over medium heat for about 5 minutes until soft and translucent.

Once the potatoes are cooked, drain and mash them in a large mixing bowl. Next, add in the sautéed onions along with 500g of ground beef. Season the mixture with salt and pepper to taste. Use a sturdy spoon or your hands to combine all these tasty ingredients until well blended.

Wet your hands slightly to prevent sticking and take a handful of the mixture, shaping it into oval patties approximately 2 inches long. Arrange the formed patties on a plate.

Set up a coating station with one bowl of beaten egg and another filled with panko breadcrumbs. Dip each croquette patty in the egg, then coat generously in panko breadcrumbs.

In a deep frying pan or wok, heat about 1 inch of vegetable oil to 350°F (175°C) over medium-high heat. Carefully add the coated croquettes in batches, frying them for about 3-4 minutes per side until golden brown and crispy.

Using a slotted spoon, remove the croquettes from the hot oil and transfer them to a plate lined with paper towels to drain excess oil. Allow them to cool slightly before serving.