Instructions
Here is how I usually prepare Butterfish: brine and dry.
No need to fillet them (but a bit of cutting is involved), easy cooking, and best of all you can eat everything -- including all the bones! Just make sure to thoroughly grill the fish, so the bones become crunchy and easy to eat.
(1) Clean and cut open as in the first picture. Some recipe says to use 4% saltwater when cleaning; I just use the plain tap water b/c I'm lazy.
(2) Make 15% saltwater. Ex. for 1 quart of water, add about 6 ounces of salt (or if you prefer the metric system like me, add 176 grams of salt to one liter of water). Submerge the butterfish in this solution and let it sit for about 20 minutes but no more than 25 min (second picture).
(3) Pat the fish dry with a paper towel. Place them on a rack and dry them overnight. Here, I placed them inside the fridge and it worked beautifully (third picture). But the smell could be an issue. What they need is a cold and dry place. During the NE winter, maybe this can be done outside.
To cook, I prefer simple grilling. Because of its fattiness and drying process, you can't really overcook the fish (unless you burn it down, of course). As mentioned above, grill thoroughly, aim for well-done and a bit more so that all bones become crunchy, like crackers. I usually eat everything except the head. My friend ate everything including the head!