Line 2 large baking trays with baking parchment. In a bowl, beat the butter and caster sugar together until soft and creamy. Whisk in the egg.
Sift the flour, Cocoa, Baking Powder and cinnamon on top and stir well. Using your hands, bring the mixture together to form a firm dough. Turn on to a lightly floured surface and knead until smooth and pliable.
Roll out the dough to 1/2 cm (1/4inch) thick. Using an 8cm (3 inch) long skull-shaped cutter, cut out 16 skull shapes, re-rolling the dough as necessary. Arrange on the baking trays, prick with a fork and chill for 30 minutes. (If you do not have a skull cutter then a gingerbread man cutter or circular cutter can be used).
Ten minutes before baking, preheat the oven to 180ºC (160ºC fan oven, 350ºF, gas 4). Bake the cookies for about 15 minutes until firm. Leave to cool on the baking trays for 5 minutes before transferring to a wire rack to cool completely.
To decorate, using the Red, Green, Yellow and Blue Ready to Roll Icing, and working on each colour separately, knead gently to make pliable. Dust the work surface lightly with icing sugar then roll out each colour to the thickness of a £1 coin. Using the same skull cutter, stamp out 4 skull shapes from each colour, re-rolling the trimmings as necessary. Once you have 16 icing skulls, gather up and keep the coloured trimmings for decoration.
Brush the top of each cookie lightly with honey and carefully stick the skulls on top, smoothing them in place with your fingers to ensure a neat fit.
Knead the Black Icing as above, and then roll out thinly. Cut out 16 pairs of eyes using a small round cutter, and then use either a small heart-shaped cutter or another small round cutter, stamp out 16 shapes for the nose. Re-roll the trimmings and cut out 16 small oblongs for the mouths.
Secure the shapes on top of each cookie using a little water. Roll out the Ready to Roll Colour trimmings and cut out shapes to decorate the top of the skulls – we used half flower-shapes topped with smaller flower shapes, finished with a dot of Black Ready to Roll Icing.
Pipe dots and swirls to decorate your cookies using the Designer Icing and Writing Icing. Leave to dry for about 30 minutes before serving.