In a medium bowl, stir together chicken, mayonnaise, lemon zest, and dried sage until just combined.
Spread a layer of butter onto all bread slices. On butter side of 2 bread slices, divide chicken mixture and spread in an even layer. Cover with remaining bread slices, butter side down, to make 2 whole sandwiches.
Using a long, serrated bread knife in a gentle sawing motion, trim and discard crusts from sandwiches. Cut each sandwich into 3 finger sandwiches. Serve immediately, or cover with damp paper towels, place in a covered container, refrigerate, and serve within 2 hours.
Recipe by TeaTime Magazine at https://teatimemagazine.com/wedgwood-chicken-sandwiches/