I was reminded this morning to do this, but I've been meaning to for a long time.
There is a........thing...........that some people do, which is to use condensed soup as a sauce.
It's not for me to tell you what to do, for a number of reasons, and if you like that, or you simply find it convenient, that's fine, just don't feed it to me. YEUK.
But if the reason you do it is fear of bechamel/white sauce/roux sauce then we can fix this.
Bechamel is a very basic sauce, and it was the first thing I was ever taught as an 11-year-old in HE at school. Although it has a French name, versions of it exist all over the world, and my guess is that it is a very old idea.
The principle behind it is to melt butter, add flour to make a sort of paste, then add milk to thin it back down to the thickness you want.
There are actually names for the different thicknesses, depending on your purpose, e.g. "Panada" for a very thick sauce. And you can look up measurements/proportions of the ingredients to predict accurately in advance how thick it will be, and your total yield. These usually keep the milk quantity stable, while adjusting the amount of butter and flour. Here's a handy olde fashionde chart to give you an idea.
Thin sauce 1/2 oz butter, 1/2 oz flour, 1/2 pint milk
Pouring sauce 3/4 oz butter, 3/4 oz flour, 1/2 pint milk
Coating sauce 1 oz butter, 1 oz flour, 1/2 pint milk
Very thick sauce 2 oz butter, 2oz flour, 1/2 pint milk
If you stick to these for quantities you will have consistent results.
But I rarely measure it. I do it by eye and I'm going to teach you how to do it.
First get a "knob" of butter. How much is a knob? It's described in cooking glossaries as a walnut sized piece, or about a rounded tablespoon. I've even seen it given as 25 grams, and that's just silly. Decide on your own knob, and stick to it. Roughly.
I did this by eye and it came to 28grams.
Melt this in a saucepan. You don't want it too hot, but you don't want to wait all day so on a scale of 10, 5 is a good heat. Let it completely melt, but don't let it start to burn.
Now, with a wooden spoon, stir in enough flour to make it all stick together. For this amount of butter a heaped tablespoon of flour is roughly right. There is considerable variation possible here, but I'll show you what exactly equal parts (by weight) butter and flour look like.
This is your roux. A mixture of fat and flour, that is now heating through, but again, you don't want it to change colour, so keep it moving about. Cook it in this way for about 1 minute.
Now add milk. The trick is to pour slowly and mix fast. Use your dominant hand to mix and your other one to pour. Slowly means slowly. Not a trickle, but a slow pour. Switch to a whisk as soon as you can, and mix FAST. When all the milk is added, keep whisking, as the mixture will thicken a little more once the heat stabilizes. Some people use warm milk to minimize that, but it isn't necessary.
So let's recap in brief.
Pour milk in SLOWLY, and whisk it FAST.
That's it. That's all there is to it.
#1 Too dense a roux, due to too much flour in proportion to fat. This is not insurmountable, and is sometimes deliberately done to get a lower fat sauce. You'll just have to whisk like a mad thing.
#2 Sauce comes out too thin. Too much milk added. If you are adding it slowly this will not happen. So pay attention.
#3 Sauce too thick. So add more milk. End of problem.