I started with this recipe , but simplified it because I don't always need it to be gluten-free or dairy-free. All I know is that it is just plain yum! The following will substitute for one can in a recipe. I'd use chicken broth in place of the milk (and omit the mushrooms, of course) if I needed a can of cream of chicken soup instead.
Add: 1/4 cup of chopped mushrooms
Cook until the mushrooms are soft and season with onion salt, if desired.
Add: 1/4 cup of flour
Whisk it in and cook slightly so the soup doesn't have a floury taste.
Add: 1 cup of milk
Whisk it in slowly so you don't get lumps. Cook and stir constantly until desired thickness. Season with salt and pepper to taste.