Prepare Meatballs:
In a bowl, mix ground beef, pork, breadcrumbs, onion, egg, milk, garlic powder, Worcestershire sauce, ½ tsp salt, and pepper.
Form into 1.5-inch meatballs (about 24 total).
Brown Meatballs:
Heat skillet over medium heat. Brown meatballs in batches. Do not fully cook—just sear.
Slow Cooker Setup:
Place meatballs in the slow cooker.
Make Gravy:
Melt butter in a skillet. Stir in flour to make a roux. Gradually whisk in beef broth until smooth.
Pour gravy over meatballs in the cooker. Add cream of mushroom soup mix.
Cook:
Cover and cook on low for 4–5 hours.
Serve:
Boil egg noodles according to package instructions (8–10 minutes).
Stir sour cream into the meatball mixture. Serve meatballs and gravy over noodles.