Prep Slow Cooker: Lightly grease the inside of a 5- to 7-quart slow cooker with a bit of oil or nonstick spray to make cleanup easier.

Add Mushrooms: Spread the sliced mushrooms evenly over the bottom of the slow cooker; they’ll soften and soak up the juices as the beef cooks.

Add Beef: Place the beef stew meat or chuck chunks on top of the mushrooms in an even layer, breaking up any pieces that are stuck together so everything cooks evenly.

Mix Sauce: In a medium bowl, stir together the condensed cream of mushroom soup and the dry onion soup mix until well combined and smooth. You don’t need to add water; the beef and mushrooms will release plenty of liquid as they cook.

Pour Sauce: Pour the soup and seasoning mixture evenly over the beef and mushrooms, using a spatula to spread it so all the meat is coated in the mixture. Do not stir; just let it sit in layers so the beef slowly braises underneath.

Cook: Cover the slow cooker with the lid and cook on LOW for 7 to 8 hours, or until the beef is very tender and easily falls apart with just a fork. Avoid lifting the lid too often, as that lets out heat and can lengthen the cooking time.

Stir & Adjust: Once the beef is fork-tender, gently stir the mixture in the slow cooker to combine the meat, softened mushrooms, and the now-rich brown gravy. If the gravy seems too thick for your liking, you can thin it with a few tablespoons of warm water or beef broth; if it’s a bit thin, let it cook uncovered on HIGH for 15 to 20 minutes to reduce slightly.

Season & Serve: Taste the gravy and add a small pinch of salt and black pepper only if needed; the onion soup mix is quite salty on its own, so many times no extra seasoning is necessary. Turn the slow cooker to the WARM setting until ready to serve. Spoon the mushroom beef tips and plenty of that glossy brown gravy over mashed potatoes, noodles, or rice, making sure each serving gets a good mix of tender beef and soft mushrooms.