Peel and cut the potatoes into 1-inch cubes.
In a large pot, cover the potatoes with cold water and bring to a boil over high heat.
Reduce the heat to medium-low and simmer until the potatoes are tender, about 15-20 minutes.
Drain the potatoes and return them to the pot.
In a small saucepan, melt the butter over medium heat.
Whisk in the flour and cook for 2-3 minutes, stirring constantly, to make a roux.
Gradually whisk in the milk and cook until the sauce thickens, about 5-7 minutes.
Season the bechamel sauce with salt and pepper.
Add the bechamel sauce to the cooked potatoes and mash until smooth and creamy.
