In a big mixing bowl, add pork, lamb, ground round, spinach, cheese, egg, basil, parsley, garlic powder, salt, red pepper flakes, and 1/4 cup of bread crumbs.
Use your hands to mix all the ingredients together until they are well incorporated.
You can either use the mixture immediately or keep it in the fridge for up to 24 hours.
Put the remaining 1/4 cup of bread crumbs into a small bowl.
Use a scale to weigh the meatballs into 1.5-ounce portions and place them on a sheet pan.
Shape the meatballs into rounds using your hands and then roll them in the bread crumbs.
Put the meatballs in individual miniature muffin tin cups.
Bake them in the oven for 20 minutes or until they are golden and fully cooked.