Preheat oven to 350℉. In a small sauce pan, melt butter over low heat.
Mix in the flour and stir until incorporated. Add the milk and stir well with a whisk.
Add salt and cayenne pepper for flavor. Continue to cook sauce on low heat until it boils, stirring occasionally with a whisk. Remove pan from heat and add 1 cup of cheese. Stir well until all the cheese is melted and the sauce is smooth.
Spread half of the thinly sliced potatoes in an 9×9″ baking pan that has been sprayed with non-stick cooking spray. Pour half of the cheese sauce over the potatoes. Repeat with the rest of the potatoes and cheese sauce and top with the remaining grated cheese.
Sprinkle paprika on top and bake uncovered for 1 hour.
Notes
Try to slice your potatoes thinly so they cook evenly.