Prep your ingredients: Slice the mushrooms, chop the onion, and mince the garlic. Soften the cream cheese so it blends smoothly later.
Brown the beef: Heat a large skillet over medium-high.
Add the ground beef and season with salt and pepper. Cook, breaking it up, until well browned and most liquid has evaporated, about 6–8 minutes. Transfer to a plate, leaving a little fat in the pan.
Sauté the aromatics: Add butter to the skillet.
Stir in the onion and cook until translucent, 3–4 minutes. Add the mushrooms with a pinch of salt and cook until browned and their moisture cooks off, 6–8 minutes. Stir in the garlic for 30 seconds until fragrant.
Deglaze and build flavor: Pour in the beef broth.
If using, add a splash of dry white wine. Scrape up browned bits. Stir in Worcestershire, Dijon, smoked paprika, and onion powder.
Simmer 3–4 minutes to reduce slightly.
Thicken the base: Reduce heat to medium-low. Whisk in the cream cheese until fully melted and smooth. If you want a thicker sauce, sprinkle in xanthan gum very lightly (start with a tiny pinch), whisking constantly to avoid clumps.
Bring it together: Return the browned beef and any juices to the skillet.
Simmer 2–3 minutes to marry the flavors. If the sauce looks too thick, loosen with a bit more broth or a splash of heavy cream.
Finish with sour cream: Turn the heat to low. Stir in the sour cream until creamy and well combined.
Do not boil after adding sour cream to prevent curdling. Taste and adjust salt and pepper.
Garnish and serve: Sprinkle with chopped parsley. Serve over cauliflower mash, zucchini noodles, sautéed cabbage, or your favorite keto base.