The secret is in the heat.

Basic Cream Sauce, also known as White Sauce, is used for dishes such as homemade macaroni and cheese.
2 tablespoons of butter
2 tablespoons of flour
1 cup of milk
The secret is to heat the butter over medium-low heat, then sprinkle in the flour, stirring continuously until a smooth paste forms. Gradually add the milk slowly, whisking the entire time. Keep the heat on medium-low and allow the milk to heat gradually. Whisk the entire saucepan, making sure to keep the bottom of the pan well-whisked. This will prevent lumps from forming as the mixture heats. Continue to whisk until you have that smooth, satiny cream sauce you were striving for. A smooth, beginner-friendly cream sauce, ready to enjoy with whatever recipe awaits.