Preheat the oven to 180°C (350°F). Line a 6-cup cupcake tin with 6 cupcake liners.

Combine 60 ml milk with 5 ml brewed coffee in a small mixing bowl. Set the coffee-milk mixture aside.

Beat 60 g unsalted butter with 30 g caster sugar and 30 g brown sugar until the mixture is light and fluffy.

Add 1 egg and 5 ml vanilla extract to the butter mixture. Beat until fully incorporated.

Add 60 g all-purpose flour and 2 g baking powder to the batter. Fold gently with a rubber spatula until just combined.

Pour in half of the coffee-milk mixture. Fold only until incorporated.

Add the remaining coffee-milk mixture. Fold gently until the batter is smooth without overmixing.

Divide the batter evenly between the 6 cupcake liners, filling each liner about two-thirds full.

Bake at 180°C (350°F) for 12 to 14 minutes. Check doneness by inserting a skewer into the center; it should come out clean.

Remove the cupcakes from the tin. Cool completely on a cooling rack before adding frosting.

Beat 115 g mascarpone cheese with 30 g powdered sugar until smooth. Add 120 ml heavy whipping cream.

Whip the mascarpone mixture until it forms firm, pipeable peaks. Transfer the frosting to a piping bag.

Pipe the whipped mascarpone frosting onto the cooled cupcakes. Dust each frosted cupcake with 2.5 g cocoa powder through a fine-mesh sieve.