Prepare the Oven and Batter: Preheat your oven to 180°C (160°C fan) and line a 12-hole muffin tin with paper cupcake liners. In a medium bowl, whisk together the plain flour, baking powder, and salt. Set it aside.

Cream the Butter and Sugar: In the bowl of a stand mixer fitted with the paddle attachment, or using a hand mixer, beat the room-temperature butter and caster sugar on medium-high speed for about 3-4 minutes, until it becomes pale, light, and fluffy.

Add Eggs and Vanilla: Scrape down the sides of the bowl. Add the eggs one at a time, beating well after each addition until fully incorporated. Mix in the vanilla extract.

Combine Wet and Dry Ingredients: Reduce the mixer speed to low. Add the flour mixture in three parts, alternating with the milk in two parts, beginning and ending with the flour. Mix only until the last streaks of flour have disappeared – be careful not to overmix. I find that a final gentle fold with a spatula ensures everything is combined without toughening the batter.

Bake the Cupcakes: Evenly divide the batter among the 12 cupcake liners, filling each about two-thirds full. Bake for 18-20 minutes, or until a skewer inserted into the centre of a cupcake comes out clean.

Cool and Prepare the Syrup: Let the cupcakes cool in the tin for 5 minutes before transferring them to a wire rack to cool completely. While they cool, prepare the syrup. Stir the sugar (and optional liqueur) into the hot espresso until it has completely dissolved.

Soak the Cupcakes: Once the cupcakes are completely cool, use a pastry brush to gently brush the tops with the coffee syrup. Don't drench them; we want them moist, not saturated. A couple of brushes per cupcake is usually enough.

Make the Mascarpone Frosting: In a cold bowl, combine the cold mascarpone, cold double cream, sifted icing sugar, and vanilla. Using a stand mixer with the whisk attachment or a hand mixer, start on low speed and gradually increase to medium-high. Whip for 2-3 minutes until stiff peaks form. Be careful not to over-whip, or it can split.

Decorate and Serve: Transfer the frosting to a piping bag fitted with a large star or round nozzle. Pipe a generous swirl onto each cupcake. Just before serving, use a small sieve to dust the tops lightly with cocoa powder.