Heat a few tablespoons of the oil in a cast iron skillet. Meanwhile, mix mashed potatoes, egg and green onions in a bowl. Put some flour on a plate and season with salt and pepper. Scoop the mashed potato mixture with an ice cream scoop and drop it into the flour, tossing to coat. Tap off excess flour, and add to skillet, pressing down on the top slightly with a spatula. Repeat with remaining mashed potatoes.

Meanwhile, mix the sour cream, dill, capers and juice, red onion, salt and pepper in a bowl, reserving a bit of the dill, onion and capers for garnish. Once potatoes are nice and brown, flip to cook the other side, adding more vegetable oil as needed.

To serve, place a dollop of the sour cream mixture on each pancake, top with a slice of smoked salmon, and garnish with a bit more sour cream, some dill, onion and capers. Enjoy!