Peel the potatoes and onion, and discard the peels. Using the large holes of a box grater, grate the potatoes and onion. Place the grated potatoes and onion in a colander. Let stand for 5 minutes. Using your hands, gently squeeze the potatoes and onions to drain off excess liquid.
Place the drained potatoes and onion in a large mixing bowl. Add the egg and stir to combine. Add the flour, salt, and pepper and stir to combine.
Preheat the oven to 200°F with a baking sheet inside. Line a plate with paper towels.
Heat 1/4 inch of oil in a large skillet over medium-high heat. Working in batches, scoop four 1/4 cup mounds of potato mixture into the hot oil, and flatten with the back of a spatula to form pancakes.
Fry on each side until golden brown, about 3 minutes per side. Remove pancakes and place them on the paper towels to drain for a couple of minutes. Then transfer the pancakes to the baking sheet in the oven to keep warm until ready to serve. Repeat with the remaining potato mixture. Serve pancakes topped with sour cream and sprinkled with chives.
Notes
The pancake mixture will turn gray or brown as it sits, so I don’t advise making it too far in advance. A couple of hours should be fine if plastic wrap is pressed to the surface and tightly covered.
You’ll want to remove as much moisture as possible from the potatoes so they’ll hold their shape and crisp up in the oil. You can put the shredded potatoes in a kitchen towel or cheesecloth and squeeze them out as much moisture as possible. They’re also more likely to fall apart if there’s too much moisture.
Make sure the oil is hot, or the potatoes won’t cook through before the exterior is crispy and brown.
Avoid adding too many scoops of the potato mixture into the oil at once. If you add too many, it’ll decrease the temperature of the oil. Tightly packing the potatoes into the skillet will also cause them to steam instead of crisping up. It’s also easier to flip the pancakes in the skillet if you don’t overcrowd it.
Add more oil as you need it to cook the pancakes. Just make sure you allow the oil to get hot before adding the pancakes to it.
If you’re not a fan of serving potato pancakes with sour cream, try serving them with applesauce or yogurt.
You can fold a little bit of shredded cheddar cheese for a cheesy version of these pancakes.