01 -
Preheat oven to 180C/160C fan-forced. Grease a 20cm square cake pan and line the base and sides with baking paper.
02 -
Mix milk and coffee in a large jug until the coffee dissolves. Add vegetable oil, eggs, and 125ml (1/2 cup) water, stirring until combined.
03 -
Sift flours, caster sugar, cocoa, and bicarbonate of soda into a large bowl. Make a well in the center, add the milk mixture, and stir until smooth. Pour into the prepared pan and smooth the surface.
04 -
Bake for 55-60 minutes or until a skewer inserted into the center comes out clean. Cool in the pan for 5 minutes before transferring to a wire rack to cool completely.
05 -
Bring cream and 125ml (1/2 cup) milk to a boil in a saucepan. In a separate bowl, mix sugar and cornflour, whisk in the remaining milk, egg yolk, peppermint extract, and green food colouring until smooth. Gradually add the hot milk mixture, whisking continuously. Cook over medium heat, stirring, for 3-5 minutes until thickened. Cover with plastic wrap and let cool for 1 hour.
06 -
Use the end of a wooden spoon to poke holes halfway through the cake. Pipe the mint custard into the holes using a piping bag fitted with a round nozzle.
07 -
Beat cream, icing sugar, and peppermint extract with electric beaters until firm peaks form, adding green food colouring to tint. Spread over the cake and decorate with Aero chocolate shards and mint chocolate balls.