Heat a saucepan on a low heat, melt butter, then stir in the brown sugar, treacle, salt, and spices.
Transfer the mixture to a medium-sized mixing bowl, allow to cool, and beat in the egg.
Whisk the baking powder and soda into the flour, and then stir these dry ingredients into the wet mix.
Divide the dough in half, and wrap well.
Get out several baking sheets; there's no need to grease them, though lining with parchment saves effort on cleanup.
Once the dough has chilled, take one piece of dough out of the refrigerator, and flour a clean work surface, and the dough. Roll it out as thin or thick as you like; for slightly less crisp cookies, roll it out more thickly. – To stop the dough from sticking, flour under and on top as you roll.
Bake the cookies just until they're slightly brown around the edges – 8 to 12 minutes, or until they feel firm.
Allow the cookies to cool for several minutes, before transferring them to a rack to cool completely. Repeat with the remaining dough.
Decorate the cookies as per your choice. I like to use Royal Icing for piping, and the addition of some candies/sweeties!