Preheat the oven to 180°C (350°F) fan-forced. Line two baking trays with parchment paper. The paper should lie flat — if it curls, crumple it into a ball first, then flatten it out.

Cream the butter and sugar together in a large mixing bowl until the mixture looks pale yellow and fluffy, about 3 minutes with a hand mixer. When you rub a tiny bit between your fingers, you shouldn't feel any graininess from the sugar.

Beat in the egg and vanilla extract until the mixture is smooth and glossy. Stop to scrape down the sides of the bowl with a spatula — you'll see streaks of butter and egg that need incorporating.

Whisk the flour, baking powder, bicarbonate of soda, and salt together in a separate small bowl. Add the dry ingredients to the wet mixture in three additions, alternating with the milk. Start with flour, then half the milk, then flour, then the rest of the milk, then the last of the flour. The dough will look shaggy and slightly sticky, but it should hold together when pressed with your fingers.

Scoop tablespoon-sized balls of dough onto the prepared baking trays, spacing them about 5cm apart. I use a cookie scoop for even sizes, but two spoons work fine. The dough balls should look rounded and slightly bumpy on the surface.

Bake for 9–11 minutes — the edges will look set and have a very light golden colour, but the centres should still look pale and slightly underdone. You'll smell a sweet, buttery fragrance when they're ready. The tops should spring back gently when touched.

Cool the cookies on the tray for 5 minutes — they'll look soft and puffy. Then transfer them to a wire cooling rack. You'll hear a slight sizzle as they hit the cool rack. Let them cool completely before frosting, about 20 minutes.

Make the frosting while the cookies cool: Beat the softened butter until creamy and pale, about 2 minutes. Gradually add the sifted icing sugar, then the milk, vanilla, and salt. Beat on high speed for 2 minutes until the frosting is light, fluffy, and spreadable. It should hold a soft peak when you lift the beaters.

Spread or pipe the frosting onto the cooled cookies. I use a small offset spatula for a rustic look, or a piping bag with a star nozzle for something fancier. The frosting should sit on top without sliding off.

Let the frosting set for 20 minutes at room temperature. The surface will develop a thin, matte crust while the inside stays soft. If you can't wait, nobody will judge you for eating one warm.