Preheat the oven to 160?C fan / 180?C conventional. Line a cupcake tin with 12 muffin cases.

Cream the butter and sugar together until light and fluffy.

Add the eggs one at a time, beating well between each until well combined.

Add the flour, cocoa powder, milk and boiling water. Fold until the mixture is smooth and combined.

Divide evenly between the muffin cases, filling each one 3/4 full.

Bake for 20-25 minutes until the cupcakes have risen and the middle of the sponge springs back when lightly pressed. Leave in the tin for 5 minutes, then transfer to a wire rack and allow to cool completely.

Beat the butter until soft and pale in colour. Sift in the icing sugar, add the milk and vanilla extract. Beat well until the buttercream is soft, creamy and smooth.

Scoop half of the buttercream into a piping bag fitted with a large open star nozzle.

Add a few drops of yellow food colouring to the remaining buttercream and mix until the colour is even. Scoop the yellow buttercream into a piping bag fitted with a large leaf-tip piping nozzle.

Pipe a swirl of white buttercream on top of each cupcake, moving in a circular motion from the outside in.

Place a mini Oreo in the middle and lightly press down to stick it to the buttercream.

Hold the piping bag horizontally with the pointy part of the nozzle facing upwards. Starting from the outside edge of the buttercream swirl, squeeze gently as you pull the bag away sharply to make a petal shape. Pipe a circle of petals all the way around, then continue to pipe another circle further in to layer the petals.