Spray your slow cooker with nonstick spray to prevent sticking.
Add the beef stew meat, cream of mushroom soup, onion soup mix, and mushrooms to the crockpot. Stir to combine.
Cover and cook on low heat for 6 to 8 hours, until the beef is fork-tender and infused with flavor.
About 30 minutes before serving, stir in the softened cream cheese and mix until fully melted. Add sour cream and stir until smooth and creamy.
Taste and season with salt and pepper.
If the sauce is too thin, thicken it with xanthan gum mixture (for low carb) or cornstarch slurry.
Serve hot over your choice of egg noodles, mashed potatoes, riced cauliflower, or veggie noodles.
Garnish with chopped parsley or thyme if desired.