In a stand mixer fitted with a paddle attachment, cream butter and sugar on medium speed for 3 minutes until aerated.

Add the egg and vanilla extract, mixing until fully emulsified.

Sift together flour, baking powder, and salt; incorporate into the butter mixture on low speed until a cohesive dough forms.

Divide dough into two discs, wrap in plastic, and refrigerate for 60 minutes to hydrate the flour.

Preheat oven to 175°C (350°F) and prepare baking sheets with parchment paper.

Roll dough on a lightly floured surface to a uniform 6mm thickness.

Cut shapes using an egg-shaped cookie cutter and transfer to prepared sheets, spacing 2cm apart.

Bake for 9-11 minutes or until the structure is set but before browning occurs.

Whisk confectioners sugar, meringue powder, and water for 5 minutes until stiff peaks form; adjust consistency with water for flood-work.

Apply decorative icing patterns to completely cooled cookies and allow 6 hours for icing to fully dehydrate.