Basic Bechamel Sauce

Directions

1. 1
   Melt butter in a heavy saucepan over moderately low heat
2. 2
   Add onions and cook, while stirring, until softened (about 2 minutes)
3. 3
   Add flour and cook, whisking, for 3 minutes to make a roux
4. 4
   Add milk in a steady stream, whisking constantly, and cook until thick and smooth
5. 5
   Whisk in salt and pepper and simmer until thickened to a desired consistency, whisking frequently
6. 6
   Pour sauce through a fine mesh sieve into a bowl and discard the solids