When I was a kid Mom would fry the gizzards, no pre-boiling. They were pretty stringy but when you are feeding five kids with one bird you use it all and it gets eaten. I use the gizzard in my broth, slow cooked for a long time. When I pick the meat off the carcass to use in tacos, salads, or soup, I reward myself by eating the gizzards and heart. They make a nice snack.