Peel and dice raw potatoes and onion if you are using a food processor or blender. Leave them whole if using a box grater.
Pulse potatoes, onion and garlic in the food processor or blender until almost pureed. If you are not using a food processor or blender, grate the potatoes, garlic and onion on the ﬁne rasp of a box grater.
Add eggs and pulse once or twice to mix, or beat with a whisk.
Mix ﬂour, baking powder, salt and pepper in a small bowl and add to potato mixture. Pulse once or twice to mix. You should have a fairly thick batter -- it should kind of plop off the spoon, not run off). Add more ﬂour if necessary.
Heat a large skillet (preferably non-stick) on medium to medium-high with about ¼" vegetable oil.
Ladle batter into skillet, making about 4 pancakes at a time, using about ¼ cup batter for each pancake. Fry until browned, turning to brown on both sides. You may need to add a bit of oil between batches.
Serve deruny while hot with a dollop of sour cream.