Heat a saucepan. Keep the flame to a low and add 2 tablespoons butter.
When the butter melts and starts to bubble, then add 1 tablespoon whole wheat flour or 2 tablespoons all-purpose flour.
Using a wired whisk, stir the flour quickly as soon as you add it. Keep on stirring so that no lumps are formed.
The frequent stirring helps the flour to cook evenly.
You will see the flour frothing and bubbling up while stirring. Sauté the flour till you get a nice cooked aroma from the flour and a pale golden color. Don't brown the flour.
Keep the flame to the lowest and then pour 1 cup chilled milk in a gentle stream. Pour the milk with one hand and stir the sauce mixture with the other. The milk has to be chilled, so that lumps are not formed. If you use hot or warm milk or milk at room temperature, lumps can be formed.
Do stir frequently while the milk warms and heats up.
On a low flame, simmer the sauce till it thickens.
When the sauce has thickened well and coats the back of a spoon, switch off the flame.
Keep the saucepan down and add the seasonings - ¼ teaspoon black pepper powder, a generous pinch of nutmeg powder or grated nutmeg and salt as required. For a cheese sauce, you can add 2 tablespoons of grated cheddar cheese.
Mix very well. The white sauce is ready and can be used for pasta or baked veggie dishes or soups. Do note that on cooling white sauce will thicken more. So you can keep the consistency accordingly.
Black pepper powder can be added less or more as per your taste.
You can skip nutmeg powder if you want.
Almond milk can be used instead of dairy milk.
Olive oil can be used instead of butter.
Do use chilled or cold milk so that lumps are not formed.