Directions

1. Beat together the butter and sugar until pale and creamy, then beat in the yolk, vanilla and zest. Sift the flour and salt into the bowl, then stir in to make a soft dough. Split into two flat discs, then wrap in cling film and chill for 30 mins, or until firm but not rock hard. Meanwhile, heat oven to 180C/160C fan/gas 4. Line two baking sheets with baking parchment.
2. Flour the work surface, then roll the dough to 5mm thick. Stamp the dough with an 8cm round cutter, then re-rolling any trimmings. Using the same cutter, cut a crescent moon and a pointy oval shape from each circle. Pinch the corners of the oval and indent the top and bottom to make lips. For moustaches, shape the half moon, pressing a dent into the top of the curve, then tweak and pinch the ends to make a moustache.
3. Chill for 10 mins, or until firm, then poke cake pop sticks carefully into the dough. I find putting one hand on top of the dough as I insert the stick with the other prevents the stick from popping through the surface of the dough.
4. Bake for 12 mins, one tray at a time, until pale golden. Leave on the tray for 5 mins before lifting to a wire rack (use a palette knife rather than the sticks) and cooling completely. Make the icing by beating the egg white and the sugar until thick and smooth. Divide into four batches and colour them two shades of pink and two of brown. Spoon the darker icings into disposable piping bags and snip off the tips (or use a number 2 nozzle).
5. Pipe moustache and lip outlines onto the cookies. Dry for a few mins. Now loosen the paler icings with a few drops of water until runny. Spoon a little onto each cookie and let it flood to the outline, nudging it up to the edge if needed, using a cocktail stick or tip of a teaspoon. Dry for 10 mins, then pipe a darker mouth line onto the lips, and zig-zagged lines over the moustaches. Sprinkle with glitter if using, and leave to set.