Ring stock and water to the boil in a small, shallow frying pan; add chicken, simmer gently, uncovered, for about 15 minutes or until chicken is just cooked through, turning halfway. Remove from heat; cool. Chop chicken coarsely and transfer to a medium bowl.
Add remaining ingredients, except bread, to chicken; stir until combined. Divide mixture evenly among 8 slices of bread. Top with remaining slices.
Slice the crusts from the sandwiches and cut each sandwich into 3 ribbons.
Not suitable to freeze. Not suitable to microwave.
To keep sandwiches fresh when making ahead, sprinkle the top of them with shredded lettuce, then cover tightly with plastic wrap.