Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
In a large mixing bowl, combine ground beef, breadcrumbs, milk, Parmesan cheese, egg, minced garlic, salt, pepper, and dried Italian herbs. Mix until just combined.
Form the mixture into small meatballs (about 1 inch in diameter) and place them on the prepared baking sheet.
Bake the meatballs in the preheated oven for about 15-20 minutes, or until cooked through and browned on the outside.
While the meatballs are baking, heat the olive oil in a large skillet over medium heat.
Add the chopped onion and sliced mushrooms to the skillet, sautéing until softened and the onions are translucent (about 5-7 minutes).
Stir in the beef broth and Worcestershire sauce. Bring to a simmer and cook for an additional 5 minutes.
Lower the heat and stir in the sour cream and Dijon mustard. Mix well until heated through. Season with salt and pepper to taste.
Once the meatballs are done, gently add them to the sauce, stirring to coat.
Serve the meatball stroganoff over egg noodles or rice, garnished with fresh parsley.