Shred potatoes on a box grater; rinse in cold water until mostly clear.

Twist shreds firmly in a clean towel until dry and loose.

Heat oil and butter on a large griddle over medium-high. Scatter potatoes into 4 thin portions.

Season with salt and pepper. Cook undisturbed 6 to 8 minutes until undersides form a deep brown crust.

Flip in sections; cook 5 to 7 minutes until undersides are crisp and centers tender.