Preheat your oven to 425°F (220°C).
Wash and dry the potatoes. Slice them thinly across the width without cutting all the way through.
Place the potatoes on a baking sheet lined with parchment paper.
Mix melted butter, olive oil, garlic, salt, and pepper in a small bowl.
Brush the mixture generously over the potatoes, making sure to get between the slices.
Bake for 45–55 minutes until the edges are crispy and golden brown.
Sprinkle with chopped parsley and Parmesan if desired before serving.