Clean trout (insert knife in anus and slit up to gills. Snipe under the lip to create a hinge of lower throat and gills and rip out all in one swoop. Scrape blood vein alone inside of spine with your finger nail to remove with water.
Take each cleaned trout and put one pat of butter on the outside of each side of the fish as you wrap up fairly tightly in a sheet of aluminum foil. Preheat grill to high. Grill foil packets on high heat for about 5 minutes per side, more if fish is 16″ or bigger, until flesh is white and flaky but not dry. Pull from fire and remove from foil.
Peel skin from top side of fish. Grab fish by tailbone and pull up from the packet, then lay the clean flesh side down on a plate and pull the tailbone back again. You will have a boneless fillet. Then using a spatula, slip the spatula between the skin (stuck on the bottom of the foil, and the other fillet and pull up and put on the plate, and you will have the second boneless fillet.
Season with salt, pepper, melted butter, tarragon, lemon, or whatever you like. My Argentinean friends like to make trout tacos with a mango salsa with this recipe.
