In a small bowl, combine the sour cream and chives; season with salt and pepper. Using a box grater set in a wide, shallow bowl, coarsely grate the potatoes and onion; stir to combine. Using your hands and working in batches, squeeze out as much liquid as possible; transfer the potato-onion mixture to a bowl. Stir in the potato starch and 1 teaspoon salt. Mix in the eggs. Transfer the mixture to a fine strainer; drain.
In a large skillet, add enough oil to measure a depth of 1/4 inch, then heat over medium heat. Working in 2 batches, scoop 1/4-cup mounds of the mixture onto a cutting board and flatten to form 3-inch-wide pancakes. Using a spatula, place the pancakes into the pan and cook, turning once, until golden, about 5 minutes; drain. Sprinkle with salt and serve with the chive sour cream.
One Quick Trick for Cutting Chives