Preheat oven to 425°F. Arrange rack in middle position.
Place potato between two chopsticks and slice vertically ⅛ inch apart, stopping before cutting through. Repeat.
Place potatoes on baking sheet.
Brush with half the butter, making sure it seeps between slices. Season with salt and pepper.
Bake 30 minutes. Gently fan slices apart and brush with remaining butter.
Bake 30–35 minutes more until crispy outside and tender inside.
Add extra salt and pepper to taste. Serve warm.
See full steps with tips & photos → https://theboatshedcafe.com/hasselback-potatoes/