Place a saucepan over low heat and add the butter. Let it melt completely, stirring occasionally, until it’s smooth and bubbly but not browned.
Once the butter is melted, add the flour to the pan. Stir quickly using a spatula or wooden spoon to combine it with the butter. You’ll notice it forms a thick paste called a roux.
Reduce the heat to low and continue to stir the roux for about 2 minutes. This step cooks out the raw taste of the flour and gives the sauce a slight golden tint. Keep stirring to prevent it from burning.
Remove the saucepan from the heat and pour in a small amount of milk (about 1/4 cup). Whisk gently but firmly to combine the milk with the roux, ensuring there are no lumps.
Return the pan to the heat and, while continuously whisking, gradually add the rest of the milk in small quantities. This slow process helps the mixture thicken evenly without clumping. Whisk steadily as the sauce begins to take on a creamy, smooth consistency.
Once the sauce has thickened to your liking, add the salt, black pepper, and grated nutmeg. Stir well to evenly distribute the seasonings and bring out the sauce’s rich flavor.
Remove the saucepan from the heat and, if desired, stir in freshly grated Parmesan cheese. The cheese will melt into the warm sauce, adding extra flavor and richness.
Your creamy Béchamel sauce is now ready to use! Pour it over vegetables, layer it into a lasagna, or mix it with pasta for a deliciously comforting dish.