In a small bowl, beat eggs and whisk together with onion, flour or matzoh meal, salt and pepper. Set aside.
Fill a large bowl with lightly salted cold water. Set aside.
Peel potatoes, leaving some skin on if you prefer. Grate half of the potatoes by hand, and shred half in the food processor (if desired.) As you work, place the finished potatoes in the salt water. (If you skip this step, your potatoes will start to discolor from being exposed to air but are still safe to eat)
Drain potatoes into a colander and press with a towel to remove as much moisture as possible. Wipe the bowl dry. Mix potatoes with egg mixture in large bowl.
Heat approximately 1/4 inch of oil in a large skillet over medium-high heat. Oil is ready when a piece of potato sizzles when it is dropped in. Drop 1/3 of a cup of batter into the oil and immediately flatten the pancake with the back of a spoon. Cook as many pancakes in the batch as will fit in one layer, frying them for 3-5 minutes per side. Add oil as needed, letting it heat up before adding more pancakes.
Place cooked potatoes on paper towels or other absorbent surface to drain. Potatoes can be kept warm in a 200 degree oven on a baking sheet. To keep crisp, do not put more than a single layer on each sheet.
Many thanks to Valerie who created this recipe, and to Izi who shared it.