Chop three of the whole gingers very finely; dice the others.
In a medium bowl, cream butter or margarine, sugar, whole egg, salt, ground ginger and finely chopped ginger.
Sift in flour; work quickly together to make a smooth dough.
Form into a ball and wrap in foil or plastic wrap.
Refrigerate 30 minutes.
Preheat oven to 400°F (205°C).
Divide dough into 3 pieces.
On a lightly floured surface, roll out 1 piece of dough at a time 1/4 inch (5 mm) thick.
Cut out oblongs 2-1/2x1-1/2 inches (6x3.5 cm).
Place on baking sheets.
Beat egg yolk with a little water; brush over cookies.
Sprinkle with diced ginger.
Bake 15 minutes or until golden.
Remove from baking sheets with a spatula; cool on a rack.