In a large bowl, combine ground beef, ground pork, breadcrumbs, milk, egg, salt, and pepper. Gently mix until just combined.
Roll the meat mixture into 1-inch meatballs.
In a large skillet, brown the meatballs over medium heat. Transfer to a baking dish.
In the same skillet, melt butter. Whisk in flour and cook for 1 minute. Gradually whisk in beef broth and heavy cream. Bring to a simmer and cook until thickened.
Pour gravy over meatballs. Bake for 20-25 minutes, or until meatballs are cooked through.