In a large mixing bowl, sift together the flour, bicarb., spices and salt.
In a free-standing mixer, cream together the butter and sugar on slow speed until light and fluffy.
Turn up to medium speed and beat in the egg, then the treacle.
Reduce the speed to low, and add the flour mixture one spoonful at a time.
Once an even dough has formed, remove from the bowl, divide into 3 equal portions and clingfilm.
Chill in the fridge, ideally overnight.
Preheat the oven to 170C, and remove one of your dough disks from the fridge to soften for 10 minutes.
Flour a clean surface and roll out the dough to a thickness of around 4mm.
Cut out Christmassy shapes and bake on a tray lined with baking parchment for 7-10 minutes, depending on the thickness of your dough and how soft / crunchy you’d like your biscuits. (Less time for soft, more for crunchy).
Turn out onto a wire rack to cool completely before decorating.
Whisk the egg whites together with the vanilla extract until frothy. Sift in the icing sugar, one cup at a time, beating well after each addition until smooth.
Beat on a high speed for 5 minutes until thick and glossy.
At this point, add food dye if you’re using it, then spoon into an icing bag and pipe directly onto your biscuits.
Nutritional Information per medium-sized biscuit without icing:
Calories: 38 / Protein: 1g / Carbohydrate: 5g / Fat: 2g / Fibre: 0g