Although they're seldom thought of as a premier culinary fish, mullet are cherished by coastal dwellers around the world for their firm, lightly fatty flesh and their roe. Mullet vary in size and color, but they all have a broadly similar anatomy and can be cleaned the same way. Although they can be baked whole, the simplest preparation method is to fillet them. This has the advantage of keeping the roe or milt intact, if present, and makes it easy to cut away the strongly-flavored belly meat.
Lay the mullet on your cutting board, and grip the tail with a clean kitchen towel. Scale the fish by scraping from the tail to the head with your knife blade, or a scaling tool if you have one. Turn the fish over and repeat the process on on the other side, then use a clean paper towel to wipe away any loose scales from the fish and your cutting board. You can skip this step if you plan to skin the fillets.
Hold the mullet firmly by its midsection, and make a vertical cut directly behind the gill plate until your knife blade reaches the spine. Turn your knife to a horizontal position, and cut through the skin along the mullet's back, all the way to the tail. This frees the fillet as far as the beginning of the ribs.
Return to your starting point and cut through the pin bones and ribs, from the mullet's neck all the way to its tail. The fillet should now be freed from the backbone, connected to the rest of the fish by a broad band of belly meat. If there is roe or milt present, remove it gently and reserve it.
Turn the mullet over and repeat your two long cuts to free up the second fillet. Remove the head and skeleton, and cut away the belly meat. Part of each fillet, near the front, might have a faint yellow discoloration from bile. If so, cut that away as well.
Lay your knife flat against the fillet and slide it under the ribs and the membrane that holds them together. Cut this away in one piece with a shallow cut, keeping your blade snug against the underside of the ribs to minimize wastage. Feel for the line of pin bones running down the middle of each fillet, and pull them out with tweezers or a set of very clean needle-nose pliers.
Skin the fillets, if you wish, by making a small cut near the tail and then turning your knife to a horizontal position once it reaches the skin. Grip the end with a clean kitchen towel to keep it from slipping, and slide your knife blade between the fillet and its skin. Repeat the entire cleaning process for any remaining mullet, then cook or refrigerate the fillets immediately.
Mullet's rich but mellow flesh has a superb flavor when lightly brined and smoked.
Mullet roe is a prized delicacy in its own right in much of the world, and is often salted and dried to add a concentrated flavor to Mediterranean dishes.