Preparing the fish:
The key to achieving crispy-skinned fish lies in the preparation and drying of the skin prior to cooking. To do this, make sure that your fishmonger removes all of the scales from the skin.
After the fish has been scaled, run your finger along the skin from the head end to the tail end several times. You will notice that when running from tail to head, the skin seems slightly rough and when going from head to tail the skin feel smooth. Starting at the tail end of the skin, place the back edge (dull top) of a long knife or a cake spatula perpendicular to the skin, then lean it forward at a slight angle towards the head end. Gently but firmly run the knife or spatula from the tail end to the head end to squeeze out as much moisture from the skin as possible. Rinse and dry your knife, then run the knife back from head to tail and again rinse and dry your knife. The key here is to be gentle and not damage the flesh of the fish. Take as many passes as necessary until the skin no longer releases any liquid. Once you are satisfied that the skin is dry, make one more pass running from head to tail to smooth out the skin. Store the fish refrigerated with the skin side up and plenty of air circulation around it until you are ready to cook it.
Cooking the fish:
To cook the salmon, season the flesh side only with kosher salt. Heat the All-Clad 10″ Sauté/Fry Pan over medium high heat. Add enough canola oil to cover the bottom of the pan by about 1/8 of an inch. When the oil begins to shimmer and release wisps of white smoke, carefully lay the salmon skin side down into the hot oil, then turn the heat down.
Very gently shake the pan or use a thin spatula to “scoot” the fish a little bit just to ensure that the skin is not sticking to the bottom of the pan. Reduce the heat again to medium and cook until the bottom third of the thickness of the salmon’s flesh has been cooked through as indicated by its opaque appearance – about 3 minutes. Using a thin metal spatula to tilt the salmon portion, check to see that the skin is golden brown and crispy. If it needs more crispness, increase the heat for a few seconds and check again.
Remove the salmon from the pan and set skin side up on a plate. Pour out the excess fat and return to medium low heat. Add the butter; when it is completely melted and begins to foam, set the salmon portions in the butter flesh side down. Turn off the heat and let the salmon sit in the butter for about 1½ minutes, then remove from the pan onto a paper-towel-lined dish to remove any excess butter.
Transfer to a serving dish or individual plates and sprinkle the skin with Maldon salt.