yep, you can use mushroom soup to make gravy.
all i do is whisk in milk,- less than i would for soup-, black pepper, salt, onion powder and garlic powder and ground sage and pour it over pork chops and mashed potatoes.
we make the best pork chop gravy by allowing a few pork chops to get really brown in the broiler on a baking sheet after the others are done (we just give those ones to the cats)
and deglazing the baking sheet with a little water. then we add flour shaken up with milk, then some water and lots of black pepper. a litte salt, too. if need be, some beef base can be added for additional flavor.
i use powdered gravies a lot, too.
milk gravy is delicious. add flour to sizzling hot butter in a pan, allow to cook for a minute, whisk in salt, pepper and milk. bring to a low boil and allow to simmer for a few minutes.