MUST do it outside. Way to much smoke when you do it. HOT ass cast iron skillet, run the fish in some melted butter then a very heavy coat of your favorite blacken seasoning. I like Paul Purdomes. Next into the hot dry skillet. It will smoke like a SOB, only takes a little time on each side. Only flip once, the more you flip them the more of a chance of having your seasoning come off.