Use as a soufflé base or to bind a runny casserole.
Combine in a small saucepan over very low heat:
1 1/4 cups milk
1/4 onion (with 1 bay leaf stuck to it using 2 whole cloves)
1 pinch freshly grated nutmeg (optional)
Simmer gently for 15 minutes, uncovered, to infuse flavor into the milk. Discard the onion, the bay leaf, and the cloves. Meanwhile, melt in a medium saucepan over low heat:
3 tablespoons unsalted butter
Stir in:
3 tablespoons all-purpose flour
Cook, uncovered, stirring occasionally with a wooden spoon or spatula, over medium low heat until the roux is just fragrant but not darkened, 2 to 3 minutes. Remove from the heat and let cool slightly. Slowly whisk in the warm milk and return the saucepan to the heat. Bring the sauce slowly to a simmer, whisking to prevent lumps, and cook, stirring often and skimming any skin that forms on the surface, over low heat, without boiling, until it reaches the consistency of a thick porridge, 8 to 10 minutes. Strain through a sieve, if desired. Season with:
