Arrange the meatballs on the prepared baking sheet, leaving space between each.
In a large bowl, gently mix the ground beef, breadcrumbs, Parmesan cheese, eggs, garlic, Italian seasoning, salt, black pepper, and milk until just combined.
Scoop about 2 tablespoons of the meat mixture and flatten it gently in your palm.
Place a cube of mozzarella in the center, wrap the meat around it, and roll into a sealed ball.
Arrange the meatballs on the prepared baking sheet, leaving space between each.
Bake for 20–25 minutes, until golden and cooked through (internal temperature 160°F).
Serve warm with marinara sauce, over pasta, in subs, or as an appetizer.