Preheat your waffle iron according to the manufacturer's instructions. Lightly grease it with cooking spray or oil.
Place the grated potatoes in a clean kitchen towel and squeeze out as much moisture as possible. This step is crucial for achieving crispy waffles.
In a large bowl, combine the grated potatoes, salt, black pepper, garlic powder, onion powder, and beaten egg. If using, fold in the cheddar cheese and green onions.
Scoop about 1 cup of the potato mixture into the preheated waffle iron, spreading it evenly. Close the lid and cook for about 8-10 minutes, or until the waffles are golden brown and crispy.
Carefully remove the waffles and repeat with the remaining potato mixture. Serve immediately with your favorite toppings, such as sour cream, applesauce, or ketchup.