Preheaat oven to 350 °F, & brush a 13″x 9″ baking pan with cooking spray.Bring a large pot of water to a boil. Scrub the potatoes and put them whole in boiling water for 20-25 minutes. It does not need to be cooked completely, but it should be easily pierced with a sharp knife.Take it out of the water, let it cool, and let it work.

Meanwhile, make the cheese sauce.Melt butter in a medium saucepan over medium heat. Whisk in the flour and cook, whisking constantly, until the flour is golden brown; About two minutes.Add the milk and cook, stirring often, until thickened; about 23 minutes.Remove from heat and mix with grated cheese. Season with salt and pepper.

Gently peel the potatoes and cut them into 1/8-inch slices.
Place a third of the potatoes, overlapping in a single layer, in a baking dish, and season with salt and pepper. Spoon about a third of the cheese sauce over the potatoes. Repeat for two more layers. Pour all the remaining cheese sauce over the top layer of potatoes. Spread to ensure all potatoes are covered.

Sprinkle with 1/2 cup shredded cheddar cheese (if desired) and paprika (about 1/8 teaspoon, just for color).
Bake in the oven at 350 degrees for 20-25 minutes, or until the sauce has bubbled.

Garnish with fresh chives or parsley, if desired. Submit it right away.

Enjoy !