1. Preheat oven to 350°F and grease 9 by 13 pan
2. Bring a large pot of water to a boil. Scrub potatoes and place them, whole into the boiling water for 20-25 minutes. Cook until easily pierced by a knife. Let potatoes cool.
3. Melt butter in a medium saucepan over medium heat. Whisk in flour and cook, whisking constantly until flour is golden-brown (2 minutes). Stir in milk and cook, stirring often, until thickened, about 2-3 minutes. Remove from heat and stir in cheese.
4. Gently peel and slice potatoes.
5. Layer potatoes and cheese in 3 layers in pan.
6. Sprinkle with cheese and sprinkle with paprika if desired.
7. Bake for 20-25 minutes or until sauce is bubbly.