When I smoked that last shoulder I had a foil pan under it to catch the drippings.  I chilled that liquid so I could more easily separate the fat from the juices.  I used all the fat to make a thick gravy.  It took a lot of flour to make the roux so the gravy set up tight in the fridge.  With a spider, I dipped the cooked potato pieces from the cooking water and used that starchy water and a whisk to bring a big spoonful of that cold gravy concentrate back to life.  I really should freeze the rest of it.