First make the biscuit dough. Add the butter, muscovado sugar and treacle to a large bowl. Mix using an electric whisk on a high speed, or by hand using a balloon whisk, until smooth and fluffy.
Add the egg and spices. Mix until just combined. Add the flour and combine using your hands until it forms a ball. Turn out on to a lightly floured surface and roll out, then use cutters to stamp out tree shapes and transfer to a lined baking tray that you can fit in the fridge. Use a straw to stamp out small holes right at the top of each biscuit. Chill the biscuits for 15 minutes.
Preheat the oven to to 190C.
Bake the biscuits for 10-12 minutes, or until just beginning to colour. Allow to cool for 10 minutes on the baking tray, before carefully transferring to a wire rack.
When the biscuits are cool, transfer them to a sheet of clean greaseproof paper
Transfer each icing colour to a piping bag and snip a small opening on each. Use to pipe baubles or tinsel string onto the tree shapes.
Then thread a ribbon or string through each hole created at the top, and hang up as edible ornaments on your Christmas tree.
Decorate with edible festive sprinkles for a final touch of sparkle. If you have pets, ensure you’re hanging the biscuits high up on the tree.