Preheat the oven to 375°F (190°C).
In a large mixing bowl, combine the ground beef, breadcrumbs, milk, egg, chopped onion, garlic powder, salt, black pepper, and thyme. Mix until well combined.
Shape the mixture into small meatballs, about 1 inch in diameter.
In a large frying pan over medium heat, cook the meatballs for about 8-10 minutes, turning occasionally until browned and cooked through. Remove from heat and set aside.
Cook the egg noodles according to the package instructions. Drain and set aside.
In a separate mixing bowl, combine the sour cream and beef broth, mixing until smooth.
In the baking dish, layer the cooked noodles, followed by the meatballs. Pour the sour cream mixture evenly over the top.
Sprinkle mozzarella and Parmesan cheese over the top of the bake.
Bake in the preheated oven for 20-25 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let cool for a few minutes. Garnish with fresh parsley if desired before serving.