In a large mixing bowl, combine the pork, lamb, ground round, spinach, cheese, egg, basil, parsley, garlic powder, salt, red pepper flakes, and 1/4 cup of the bread crumbs. Using your hands, mix all ingredients until well incorporated. Use immediately or place in refrigerator for up to 24 hours.
Place the remaining 1/4 cup of bread crumbs into a small bowl. Using a scale, weigh meatballs into 1.5-ounce portions and place on a sheet pan. Using your hands, shape the meatballs into rounds, roll in the bread crumbs and place the meatballs in individual, miniature muffin tin cups. Bake for 20 minutes or until golden and cooked through.