1. Cover potatoes with water, bring to a boil, lower heat, cover and simmer until tender, about 8 minutes.
2. Drain and cover to keep warm.
3. In saucepan over medium high heat, melt butter, whisk in flour, then milk, stirring constantly until thick.
4. Season sauce with salt, black pepper and nutmeg.
5. Stir in cheese.
6. Pour sauce over potatoes and stir to coat.