Wash the potatoes and place them whole and unpeeled in a pot of water. Bring to a boil and cook for eight minutes, until partially cooked but still firm.
Drain the potatoes and let them cool until safe to handle. Peel and grate them into a large bowl.
Grate the onion into the bowl. Add the cheddar, mozzarella, flour, salt and pepper. Mix until evenly combined.
Divide the mixture into 36 portions. Roll and press each portion into a compact ball.
Preheat the waffle iron and lightly grease it with butter. Place one ball in each section and gently close the waffle iron.
Cook for three to five minutes, until golden brown and crisp. Carefully remove and serve hot with sour cream or another dip.
Notes
Don’t fully cook the potatoes before grating.
Waffle-iron temperatures and cooking times vary.
Grease the iron again between batches if needed.
Use white or orange old cheddar, or combine leftover melting cheeses.
Add chili powder, garlic powder, oregano, thyme or paprika if desired.
Reheat cooked waffles in an oven or air fryer to restore their crisp texture.