bechamel sauce

INGREDIENTS 3 tablespoons unsalted butter. 1/4 cup finely chopped onion. 1/4 cup all-purpose flour. 1/2 teaspoon coarse salt. 4 cups whole milk. Fresh nutmeg root micro planed to taste(1 TB minimum). DIRECTIONS In a medium saucepan, melt butter over medium. Add onion and cook until softened, about 6 minutes. Add flour and salt; cook, stirring frequently, until mixture is pale golden, has a slightly nutty aroma, and is the texture of cooked oatmeal, about 5 minutes. Whisking constantly, pour in 2 cups milk; add 2 more cups milk and whisk until smooth. Cook mixture, stirring constantly along the bottom of pan, until boiling, about 7 minutes. Add nutmeg to taste. Reduce heat to low. Simmer gently, stirring occasionally, until sauce thickens and does not feel grainy when a very small amount is rubbed between two fingers, about 10 minutes. Pass through a chinoise, Re season to taste. Chill and lable. Good for 3 days shelf life maximum.