Bring a large pot of water to a boil. Add whole potatoes; boil until just soft, 15 to 20 minutes.
Shred potatoes using a food processor. Transfer to a large bowl; allow to cool, about 10 minutes.
Mix Cheddar cheese, fontina cheese, seasoned salt, garlic powder, and black pepper into potatoes until well combined. Shape 2 tablespoons of potato mixture at a time into thick disk shapes.
Pour flour into a bowl. Whisk eggs together in a separate bowl. Pour panko into a separate bowl. Roll potato disks in flour, coat with egg, and roll in panko.
Heat 2 inches oil in a heavy skillet to 350 degrees F (175 degrees C). Fry tots in batches until crispy and golden, about 4 minutes. Cool on a paper towel-lined tray, about 5 minutes. Season with salt.
We have determined the nutritional value of oil for frying based on a retention value of 10% after cooking. Amount will vary depending on cooking time and temperature, ingredient density, and specific type of oil used.