Scalloped Potatoes

3 Tbs butter3 Tbs all-purpose flour2 tsp salt1/4 tsp pepper3 cups milk6 cups thinly sliced potatoes
Melt butter in a large saucepan over medium-low heat.  Stir in flour until smooth and bubbly.  Stir in salt & pepper. Gradually add milk, stirring until thick and bubbly.  Add sliced potatoes to sauce.  Cover and simmer for (approx) 8 min.Transfer mixture to a greased 12x8" baking dish.  (sprinkle top with grated parmesan cheese if desired for a crispy crust) Bake uncovered at 375˚ for (approx) 45 min