Summarize this article in one sentence.
Cut the butter into small cubes first, then put it into a small saucepan. Place the saucepan onto the stove, and turn the heat up to medium. Wait for the butter to melt, stirring it occasionally. Stir the butter and flour constantly as it's cooking to prevent scorching. Stir the sauce as you pour the milk so that it blends in. Once you have the milk stirred in, place the saucepan back onto the stove, and set the heat back to medium. Cook the sauce until it comes to a boil. Stir it often. Take the saucepan off the stove, and stir in part of the cheese. Be sure to scrape the bottom of the pan from time to time to ensure that everything mixes in evenly. Save the remaining ½ cup (50 grams) of cheese for later. If you have not already done so, wash and peel the potatoes, then cut them as thinly as your can. Spread a third of them across the bottom of your dish, overlapping the edges slightly. Repeat the potato, salt, pepper, and sauce layers two more times. Spread it as evenly as you can over the top of your potatoes. When the cheese bakes, it will form a melted, crusty layer on top. They are ready when they turn tender and golden. If the top of your potatoes start to burn, cover the dish with a sheet of aluminum foil; this will allow the potatoes to continue baking without getting burnt. They are a great size dish for just about any meat dish. They are also easily transported, making them perfect for picnics, potlucks, and parties.

Summary:
Melt the butter in a saucepan over medium heat. Stir in the flour, then cook it for about 2 minutes, or until it starts to bubble. Take the saucepan off the stove, then slowly stir in the milk. Cook the mixture over medium heat until it starts to boil. Stir in 1½ cups (150 grams) of cheese. Spread a third of your potatoes across the bottom of the dish. Season the potatoes with salt and pepper, then pour a third of the cheese sauce over them. Sprinkle the rest of the cheese on top. Bake the potatoes, uncovered, for 1 hour. Allow the potatoes to cool slightly before serving them.