Season the cubed steak with garlic powder, onion powder, smoked paprika, salt, and black pepper.
Optional: Sear the seasoned steak in hot oil until browned, then transfer to the slow cooker. Or add raw steak directly.
Layer sliced onion, mushrooms, and minced garlic over the steak. Mix beef broth, cream, cornstarch, and Worcestershire; pour over ingredients. Add thyme.
Cover and cook on LOW for 6-8 hours or HIGH for 3-4 hours until tender. Thicken gravy if desired by cooking uncovered for 30-60 minutes.
Adjust seasoning, garnish with parsley, and serve hot.
Notes
For extra flavor, brown the steak before slow cooking. Adjust gravy thickness by simmering uncovered or adding more cornstarch slurry.