Beat butter and sugar in small bowl until light and fluffy. Stir
in the treacle and egg yolk. Transfer mixture to large bowl, stir
in sifted dry ingredients. Knead dough on lightly floured surface
until smooth; cover with cling film and refrigerate for 30 minutes.
Roll dough between sheets of baking paper until 4mm think.
Cut shapes from dough using Christmas cutter. Cut a small hole in
shapes for hanging, if desired.