Cream together softened butter and golden caster sugar in a mixing bowl until light and fluffy, about 3-4 minutes. Incorporate egg yolk, vanilla extract, and lemon zest until well combined. Gradually sift in plain flour and salt, stirring gently until a soft dough forms. Wrap in plastic wrap and chill in the refrigerator for 30 minutes.

Preheat your oven to 180°C (350°F). Roll out chilled cookie dough to 5mm thickness. Cut with an 8cm round cookie cutter, then shape each into whimsical lips and moustaches. Place on a lined baking sheet and chill for an additional 10 minutes.

Insert a cake pop or lolly stick into the base of each cookie shape, ensuring they stand upright and are properly supported.

Bake cookies in preheated oven for approximately 12 minutes until pale golden. Monitor to prevent overbaking. Transfer to a wire rack to cool completely.

In a clean bowl, whisk together egg white and icing sugar until thick and smooth. Divide for coloring, adding pink and brown food coloring to achieve desired shades.

Outline cookie edges with colored icing using a piping bag fitted with a fine nozzle. Fill centers with additional icing and sprinkle with edible glitter while wet.

Use darker icing to add intricate details such as eyes and moustache curls. For extra sparkle, sprinkle on additional edible glitter. Allow icing to set completely before serving.