Put the sardines in ice water until you're ready to open them up. By chilling them, the fat in the guts will solidify, and the fish will be easier to cut and open. In addition, sardines are so tender that they fall apart under their own weigh, and the liquid that is produced is what gives them their distinctive fishy smell.

Cut off the head and remove the innards. You don't have to remove everything with your knife--just remove as much as you can. Sardines don't have scales. Sardines shed their scales when they are surprised. When they're caught in a fishing net, they get surprised and their scales drop off. You do occasionally run into one that hasn't lost its scales, though.

Run the fingernail of your thumb along the backbone, and open up the fish towards the tail with your fingers. The fish will form a V shape at this point. You don't have to force it flat.

Break the backbone off near the tail. Alternatively, you can cut the bone with kitchen scissors and rip it off. Once this bone is removed, the V-shaped fish will become nice and flat. You could also remove the bone from the head end. Use whichever method works best for you; either way, work slowly without rushing it.

Remove any black bits left by the innards and any small bones, and you're done. The butterflied sardine is clean even if you don't rinse it in water. Freeze the removed fish guts until it's time to take out the trash, so they won't smell up your kitchen.

After butterflying the sardines, put some salt in ice water so that it's about as salty as sea water, and quickly rinse the sardines in it. Place them on paper towels to drain off any excess moisture.

I put some umeboshi plum paste and a shiso leaf on each sardine, but you can just salt and pepper them or season them with yuzu pepper or curry powder. Whatever you prefer. Coat them with bread flour. It makes tempura batter or breading stick better: however, If you don't have any, cake flour is fine.

After coating the fish in flour, they are typically dredged in egg, but I used tempura flour (which has egg in it) instead. You can use only as much as you need so it's economical. Mix the tempura flour with water, and add the mayonnaise, too. The mayonnaise is a substitute for egg and oil. If you add a little oil to the coating of deep fried foods, they fry to a nice crisp. Coat with panko.

Line a shallow tray or similar with panko. Place the breaded sardines on top, and cover with more panko. I do this for croquettes too, or any breaded deep fried food. Chill in the refrigerator for at least an hour before frying.

Chilling the breaded sardines in the refrigerator will settle the coating and they'll fry up very nicely. Deep fry in 170 to 180 ℃ oil. When the moisture evaporates and the fish float to the surface, they are done. Watch out for this, as well as the color of the breading. Thoroughly drain off the excess oil.

Don't lay the freshly fried sardines flat--stand them up on end instead. When the oil has completely drained off, serve and enjoy!