Prep the crockpot: Lightly grease the insert with olive oil spray or a small pat of butter to help prevent sticking.
Layer the base: Add sliced onions and mushrooms to the bottom of the crockpot. Place the frozen meatballs on top in an even layer.
Whisk the sauce: In a bowl, mix cream of mushroom soup, beef broth, Worcestershire sauce, Dijon, paprika, garlic, pepper, and salt until smooth.
Pour and cook: Pour the sauce over the meatballs. Cover and cook on Low for 4–5 hours or High for 2–3 hours, until meatballs are heated through and tender.
Add the creaminess: About 20 minutes before serving, stir in the cream cheese until melted.
Then fold in the sour cream. Taste and adjust seasoning with salt and pepper.
Cook the noodles: Boil egg noodles according to package directions. Drain and toss with a little butter or olive oil to prevent sticking.
Serve: Spoon the creamy meatball stroganoff over noodles, rice, or mashed potatoes.
Garnish with fresh parsley if you like.