Thaw fish, if frozen. Rinse fish and pat dry with paper towels. Place fish on the greased unheated rack of a broiler pan. Sprinkle with lemon pepper seasoning.
Broil 4 inches from the heat until the fish flakes easily with a fork. Allow 4 to 6 minutes per 1/2-inch thickness of fish. Turn 1-inch thick fillets over halfway through broiling.
Alternatively, fry fish in olive oil in fry pan over medium-high heat until fish flakes easily with a fork.
Meanwhile, in a small saucepan, stir together sour cream, milk, mustard, chives and black pepper. Heat through, but do not boil. Serve over fish. Makes 4 servings.