Peel and coarsely grate the potatoes using a box grater or food processor. Place grated potatoes in a clean kitchen towel and squeeze out as much liquid as possible over a bowl. Let the liquid settle for 5 minutes, then pour off the water, keeping the white starch at the bottom.

Transfer the squeezed potatoes to a large mixing bowl. Add the reserved potato starch, finely chopped onion, eggs, flour, salt, and black pepper. Mix thoroughly until well combined.

Heat 2 tablespoons of vegetable oil in a large skillet over medium-high heat. Once hot, drop heaping tablespoons of the potato mixture into the pan, flattening each into a pancake about 3 inches in diameter and 1/4 inch thick.

Fry for 3-4 minutes on the first side until deep golden brown and crispy. Flip carefully and cook for another 3-4 minutes on the second side.

Transfer cooked pancakes to a wire rack set over a baking sheet and keep warm in a 200°F oven while preparing remaining batches. Add more oil to the pan as needed between batches.

Once all pancakes are cooked, arrange them on a serving platter. Top each pancake with a small dollop of sour cream, a folded slice of smoked salmon, a sprinkle of fresh dill, and a tiny squeeze of lemon juice.

Garnish with additional dill sprigs and serve immediately while pancakes are still warm and crispy.