Scalloped Potatoes - cooking recipe

Ingredients

3 Tbsp butter or margarine
3 Tbsp all purpose flour
1 1/2 tsp salt
1/4 tsp pepper
3 c milk
9 medium potatoes (3lbs)
2 Tbsp minced onion

Preparation

About 2 1/2 hours before serving in 2-quart saucepan over medium heat, melt butter or margarine, stir in flour, salt and pepper until blended; continue cooking 2 minutes.
Stirring constantly.
Gradually stir milk and cook until sauce is thickened and smooth, stirring constantly.
Remove pan from heat; set aside stirring occasionally to prevent a skim from forming on sauce.