Peel and cut the potatoes, then put them in a bowl of cold water so they won't turn brown. Next, grate the potatoes thru the large hole on a box grater. Add cold water to the basin, then stir the potatoes well. Drain the water after it has become murky. To release most of the liquid, move to a strainer and press. On low heat, preheat a nonstick skillet. Add the potatoes to the heated oil and cook for 5 to 6 minutes. Before continuing, drain the potatoes using an oil strainer and give them a little time to cool. Combine the salt, pepper, dry beef stock powder, and cornstarch with the potatoes in a bowl. Put ¼ cup of the mixture on a piece of parchment paper. Make it flat, like a rectangle shape. Add another 2–3 tablespoons of potatoes on top, and then fold the parchment paper over the top to make it flat. You can make the patties with the help of paper. Do the same thing with the rest of the mix. Add the oil to a nonstick skillet that has been heated to medium-high. Add the hashbrowns to the skillet and cook them for a few minutes, turning them occasionally, until golden brown all over.