The secret to successful butterfish cookery is do not overcook. Whichever of the following cooking methods you choose, your butterfish will be cooked when its flesh becomes opaque but is still moist, and can easily be pierced with a fork. For grilling and frying, leave scales on but cut off the head and tail with a sharp knife. For baking and poaching, rub off the small scales with your fingers.
Place butterfish in a greased baking dish or wrap in oiled foil and place on a baking sheet. Brush with melted butter or oil and season with salt and pepper, or cover with a piquant sauce. Bake in a preheated 450F (230C) oven until done, about 10 minutes for each inch (2.5cm) of thickness.
Place the whole small fish directly on greased grill, 4 to 6 inches (10 to 15cm) above prepared coals or fire. Baste with butter, oil, or marinade, and close hood of grill. Cook until fish is opaque and moist on the inside, 6 to 8 minutes.
Coat butterfish with seasoned flour, crumbs, or cornmeal. Shake off extra coating and fry fish in a small amount of hot butter or oil, turning once halfway through cooking time. Cook until opaque and moist on the inside, 4 to 8 minutes.
Bring poaching liquid, consisting of water, broth, herbs, and spices, to a simmer. Slip the butterfish in, then cover pan and keep liquid at a simmer for about 8 minutes per inch (2.5cm) of thickness.