Melt the butter in a saucepan over low heat. Once it begins to bubble, add the flour and whisk continuously until a smooth, golden paste forms, about 3–4 minutes.
Gradually pour in the milk a little at a time, whisking constantly to prevent lumps. Increase the heat to medium and continue whisking as the mixture comes to a gentle boil and starts to thicken.
Reduce the heat to low and let the sauce simmer for about 5 minutes, whisking continuously until smooth and creamy.
Season with your desired spices, then stir in the herbs if using.
Serve warm with pasta or any meal you want.
