Melt the butter in a saucepan over low heat. Stir in the flour, and cook, stirring, for 3 to 4 minutes; do not brown.
In another saucepan, bring the cream just to a boil. Stir the
warm cream into the flour mixture, whisking until smooth.
Add the onions and bay leaves, and simmer for 20 minutes on low
heat. Season with salt, pepper, and nutmeg. Strain the sauce and
serve.
Recipe from "The Red Lion Inn Cookbook"
Makes 2 cups.