Melt the Butter: In a medium saucepan, melt the butter over medium-low heat. Make sure not to let it brown or burn; you want it to be melted and foamy.
Create the Roux: Once the butter is melted, add the all-purpose flour to the saucepan. Stir continuously with a whisk or wooden spoon to combine the flour with the butter. Cook the roux for about 2 minutes until it becomes a pale, smooth paste. This step is crucial to remove the raw flour taste from the sauce.
Add the chicken stock powder to the milk and give it a stir. Gradually Add the Milk: Slowly pour the milk into the roux, whisking constantly to prevent lumps from forming. Gradually incorporating the milk is essential to achieve a smooth and creamy texture. Continue whisking until the sauce thickens, which should take about 5-7 minutes.
Season the Sauce: Add the salt, ground white pepper, and a pinch of ground nutmeg (if using). Nutmeg adds a subtle warmth to the sauce, enhancing its flavor.
Simmer and Thicken: Reduce the heat to low and let the sauce simmer for an additional 2-3 minutes, stirring occasionally. The sauce will continue to thicken during this time.
Adjust Consistency: If the sauce becomes too thick, you can adjust the consistency by adding a little more milk, a few tablespoons at a time, until you achieve your desired thickness.