Preheat oven to 160C. Sift flour, baking soda and spices together with salt.
Cream butter, sugar and golden syrup in a large mixing bowl.
Add the egg and egg yolks slowly.
Add the dry ingredients in batches.
Mix thoroughly, then shape into a rectangle log. Cover with cling wrap and refrigerate for at least 3 hours.
On a lightly floured bench, roll dough out to a 3-4mm thickness. Cut out shapes and place on baking paper (off cuts can be remoulded and used again).
Bake for approximately 15 minutes until very light golden colour.
Cool on trays, then store in an airtight container until ready to use.