Grate potatoes and onions together using a hand grater or food processor. Place the potatoes and onions in a large strainer. Squeeze over a bowl, removing as much liquid as possible. Pour off liquid from the bowl allowing the potato starch to remain.
Transfer potatoes and onions into a large mixing bowl. Add remaining ingredients (except the oil) as well as the potato starch from the bowl to the potatoes and onions. Mix together well.
Line a baking sheet with paper towels. Preheat the oven to 200 degrees F to keep prepared latkes warm. Pour oil into a heavy-bottomed skillet, about ½ inch. Heat over medium heat until a bamboo skewer inserted to touch the bottom creates bubbles.
When the latke is golden brown on one side (3-5 min), carefully flip and cook on the opposite side. Transfer latkes to paper towel. If desired, sprinkle with salt. Keep warm until all latkes are cooked.