Score the fat of the chilled breasts with a sharp knife into a 1/2" hatch being careful not to pierce the meat.
Pat dry and season well with Kosher Salt and pepper. Rub the seasoning into the skin.
Drizzle a thin layer of canola oil into a cold heavy carbon steel or cast iron skillet, then place the breasts fat side down and turn the heat on to medium. Press the breasts down so the skin fully makes contact with the pan.
Render the fat render for about 20 minutes, or until the skin is crispy and most of the fat is rendered off.
Turn the heat down to low and carefully turn the breasts over to finish cooking on the flesh side. Immediately sprinkle a little more salt on the hot skin.
Cook on the flesh side for 2 to 5 minutes, depending on the size of your duck breasts. Until the internal temperature reaches 125° to 130°F for medium-rare.
Remove from the skillet and rest skin side up uncovered for 10 minutes before slicing and serving.