Place everything but the oil and salt in a medium bowl; stir to combine and set aside.

Heat half the butter in a large frying pan over medium heat until hot but not browning.

Drop 3 to 4 (1/3-cup) large spoonfuls of the potato mixture into the pan and spread each into a 3-inch patty

Fry undisturbed until the bottoms are golden brown, about 4 to 5 minutes. Gently flip the cakes and cook until golden brown on the second side, about 4 to 5 minutes more

Transfer to a plate; season with with salt and keep warm.

Repeat with the remaining potato mixture.

Serve with sour cream or gravy.