Combine breadcrumbs and milk in small bowl.
Let breadcrumb mixture soak for five minutes.
Add ground beef to large mixing bowl.
Mix in soaked breadcrumbs and beaten egg.
Add Parmesan cheese, garlic, and diced onion.
Season with salt, pepper, and fresh parsley.
Gently mix all ingredients until just combined.
Shape mixture into golf ball sized portions.
Heat olive oil in large skillet.
Brown meatballs on all sides carefully.
Cook for twelve to fifteen minutes total.
Check internal temperature reaches 165°F.