BEAT TOGETHER CREAM CHEESE and butter until smooth and light. Beat in lemon zest and salt and pepper to taste. Stir in chives. Lay out 6 slices of the bread. Carefully spread with half the filling. Place the salmon, overlapping if necessary, in an even layer over the filling. Spread with the remaining filling and top with the remaining slices of bread. Trim off the crusts and cut the sandwiches into quarters.