Special equipment: an 8-inch nonstick skillet
Set a large strainer or colander over a bowl and line it with a clean kitchen towel. Using a box grater, grate the potatoes and onion into the strainer. Using the towel, squeeze as much liquid from the potatoes and onion as possible. Transfer the mixture to another bowl and stir in the flour, eggs, chives, baking powder, salt and pepper.
Coat the bottom of an 8-inch nonstick skillet with oil and add a couple of tablespoons of butter. Heat over medium heat until the butter foam subsides. Spoon about 1 3/4 cups of the potato mixture into the pan and press to fill the circumference. Fry over medium heat, flipping once, until the pancake is golden and crisp, 3 to 4 minutes per side. Drain the pancake on a paper towel-lined baking sheet. Repeat with the remaining batter.
If your pancake breaks while flipping it, just press it back together in a baking dish, add a splash of cream and some Cheddar and bake at 350 degrees F until the cheese is melted and the pancake is brown, 15 to 20 minutes.