Tonight I cooked a dish involving chicken hearts and gizzards, but I found conflicting instructions on the internet, so I essentially parboiled the offal, diced it, and then cooked it in butter in a covered pan for probably about 20 minutes.
The texture isn't too bad, but a little rubbery. Is this normal, or did I cook it badly? What cooking method will make chicken hearts/gizzards/livers etc as tender as possible? (And will it work for other kinds of offal?)