Prepare the Potatoes and Onions: Grate the potatoes using a coarse grater. Transfer the grated potatoes to a clean kitchen towel and squeeze out as much liquid as possible. This step is crucial for achieving crispy pancakes. Grate the onion and mix with the potatoes.

Mix the Batter: In a large bowl, combine the grated potatoes and onions with the eggs, flour, salt, and pepper. Mix until all ingredients are well incorporated.

Heat the Oil: In a large skillet, heat the vegetable oil over medium-high heat. The oil should be hot enough that a drop of the potato mixture sizzles immediately upon contact.

Fry the Pancakes: Scoop about 2 tablespoons of the potato mixture into the skillet, flattening it with the back of the spoon to form a pancake. Fry for 3-4 minutes on each side, or until golden brown and crispy. Avoid overcrowding the pan; fry in batches if necessary.

Drain the Pancakes: Remove the pancakes from the skillet and drain them on paper towels to remove excess oil.

Serve: Serve the pancakes hot, with a dollop of sour cream and a spoonful of apple sauce on the side.