Preheat oven to 350°F.
In a large bowl, combine ground beef, ground pork, beaten egg, cheese, parsley, salt, and pepper. Mix together until combined.
In a separate bowl, combine the milk, breadcrumbs, garlic, and onion. Mix well.
Combine the milk mixture with the meat mixture, and mix until just combined.
With greased hands, form the mixture into 2 tablespoon-sized meatballs and place on a parchment-lined baking sheet.
Bake until the outsides are browned and they read 165°F on a meat thermometer (about 25 minutes).