I firmly believe that every cook should be able to make a basic white sauce because you can do a few things to it to create a variety of other sauces.
I know everyone has their own basic recipe. Mine is as follows:
1/4 cup butter, gently melted till just liquid.
Add 2 tblsp flour into the butter.
Mix and keep mixing over medium heat until it thickens and turns a beautiful golden color. Add 1 to 2 cups milk slowly while stirring to keep it from clotting. Keep stirring till it thickens to the proper consistency. Finish with a bit of salt and pepper. You are done. I should tell you these are general measurements because I always eyeball them as I cook.
I've seen recipes which used arrowroot, cornstarch, or potato starch to thicken the sauce. If you use one of these, you would melt the butter, add most of the milk but you would keep a 1/4 cup of the milk back to mix with the powder. Add it to the heated milk and stir till thick.
Now what can you do with the sauce? Tons of things.
1. As it is thickening, add grated cheese, keep stirring till fully melted and mixed. I often use a provolone or smoked Gouda to give it a smoky flavor. This is the sauce, I use on my macaroni and cheese dish.
2. Sometimes, I saute finally chopped mushrooms in an increased amount of butter, fish the mushrooms out, add the flour and make a thinner sauce by increasing the amount of milk. When its ready, add the mushrooms back in for a mushroom sauce to add to the pasta.
3. Add a variety of herbs in the butter as its melting and make as normal. I like this poured over eggs on toast to add a bit of flavor. Occasionally I add a sprinkle of Parmesan or Asiago just before its done to create depth.
4. Add garlic to the butter as it melts and use this white sauce in your lasagna instead of tomato sauce. I've often added chopped dried vegetables to this mixture to add more nutrition to this. Try this white sauce with Asparagus. It is good this way.
5. My mother used to make the white sauce, add it to cooked ground beef and mushrooms. She served it on noodles and called it Goulash.
6. My father likes to add vegetables and chicken to a white sauce, pour it in a pan, cover it with mashed potatoes and calls it Shepard's Pie. On the other hand, he puts a crust in a pie pan, adds the meat/veggie mixture, tops it with another crust and calls it a huge pot pie.
7. Make the mushroom sauce, add it to green beans, top with onion rings for your own version of green bean casserole.
As you can see, having a basic white sauce in your cooking repertoire is perfect because its the starting point to other fantastic dishes.
Let me know what you add to your white sauce and how you use it. I'd love to hear more.