1. Preheat your oven to 375°F (190°C) and grease a baking dish.
2. In a saucepan over medium heat, melt the butter. Whisk in the flour and cook for 1-2 minutes until golden.
3. Gradually add the milk, stirring continuously, and simmer until the sauce thickens.
4. Off the heat, stir in the sharp cheddar cheese, salt, and optional cayenne pepper until smooth.
5. Arrange half of the sliced potatoes in the prepared baking dish. Pour half of the cheese sauce over them.
6. Layer the remaining potatoes and top with the rest of the sauce.
7. Sprinkle the top with the extra grated cheese.
8. Cover the dish with foil and bake for 45 minutes. Then, uncover and bake for an additional 15-20 minutes until the top is golden and crispy.
9. Serve the scalloped potatoes hot, garnished with sliced green onions if desired.
Enjoy the creamy and cheesy goodness of these scalloped potatoes as a comforting side dish!
