Mix potatoes, cheese, beaten egg, and salt in a medium bowl until well combined. If the mixture is very wet, mix in flour as needed to bind mixture together.
Melt butter on a large griddle over medium heat. Drop potato mixture onto the hot griddle, 1/4 cup at a time. Flatten each pancake with the back of a spatula to 1/2-inch thickness. Fry until golden brown, about 5 minutes per side. Serve hot.