Step 1: Run your fingers over the fish, feeling for pin bones. Remove any you find with kitchen tweezers or needle-nose pliers. Rinse the salmon under cold running water and blot dry with paper towels.
Step 2: Pour the 1/2 cup of Scotch into a large resealable plastic bag and add the salmon. Marinate in the refrigerator for 1 hour, turning several times.
Step 3: Drain the salmon well and blot dry.
Step 4: Make the cure: Place the brown sugar, salt, and pepper in a large mixing bowl and mix with your fingers, breaking up any lumps in the sugar. Place 1/3 of the cure on the bottom of a baking dish just large enough to hold the salmon. Place the fish on top and spread the remaining cure over the fish. Cover with plastic wrap. Marinate the fish in the refrigerator for 4 hours.
Step 5: Rinse all the cure off the fish under cold water and blot the fish dry. Place it on the cedar plank.
Step 6: Set up the grill for indirect grilling and preheat to medium.
Step 7: When ready to cook, place the salmon on its plank in the center of the hot grate, away from the heat. Toss the wood chips on the coals. Cover the grill and smoke-roast the fish until cooked through, about 20 to 25 minutes. To test for doneness, insert an instant-read meat thermometer through the side: The internal temperature should be about 135 degrees. Transfer the salmon on its plank to a platter and let cool slightly.
Step 8: Meanwhile, whisk the chives and Scotch into the cream cheese. Place in a serving bowl. Lightly butter the cut sides of the bagels.
Step 9: Rake the coals into a mound for direct grilling and preheat the grill to high. Brush and oil the grill grate. Toast the bagels on the grill, rotating each after 1 minute to lay on a crosshatch of grill marks. Place the bagels in a cloth-lined basket. Serve at once. Sunday morning lox and bagels never quite tasted like this!