Step 1: Rinse off the salmon fillet and blot dry. Run your fingers over the fillet, feeling for bones. Pull out any you may find with kitchen tweezers or needle-nose pliers. Place the fish in a nonreactive baking dish just large enough to hold it. Add the whisky and marinate in the refrigerator for 30 minutes, turning the fish twice. Drain the fish well in a colander and blot dry with paper towels, discarding the whisky. Wipe out the baking dish.
Step 2: Make the cure: Place the sugar, salt, and pepper in a large bowl and mix well, breaking up any lumps in the brown sugar with your fingers. Place one-third of this mixture in the bottom of the baking dish. Arrange the fish pieces on top, skin side down. Sprinkle the remaining cure over the fish, patting it into the meat. Cover the fish with plastic wrap and cure in the refrigerator for 4 hours.
Step 3: Rinse the cure off the fish and blot dry. Arrange the fish pieces skin side down on a wire rack and dry in the refrigerator for 2 hours.
Step 4: Set up your grill for indirect grilling and preheat to low (250 degrees). (Alternatively, set up your smoker according to the manufacturer’s instructions.)
Step 5: Place the fish skin side down on the smoker racks (oil the racks or the skin side of the fish first to prevent sticking). If using a grill, add the smoking chips. Smoke the fish until golden brown, crisp at the edges, and just cooked through, about 1 hour. To test for doneness, press it with your finger—the flesh will break into clean flakes. Alternatively, insert the probe of an instant-read thermometer through the thick end of the fish into the center. The internal temperature should be 140 degrees.
Step 6: Transfer the salmon to a wire rack over a rimmed baking sheet and let the fish cool to room temperature, then refrigerate until serving. It will keep in the refrigerator for at least 3 days or in the freezer, tightly wrapped in plastic wrap, for several months. Serve with your choice of the recommended accompaniments.