Boil your chicken until cooked completely, 20-30 minutes. Then dice into small pieces.
Slice grapes in half.
Finely dice onion.
Dice jicama into half inch cubes.
Cut celery into thin slices.
Toss all of that into a bowl. Add mayo, mustard, parsley, garlic salt and lemon juice. Mix well.
Chill for at least an hour before serving.