First, make the unicorn horns and ears. Take a small ball of the black fondant icing about the size of a 20 pence piece and roll it into a sausage shape about 8cm long that is thinner in the middle and wider at the ends.
Fold the sausage in half then twist the two halves together to make a horn shape.Place on a piece of baking paper, then repeat until you have 12 unicorn horns. Leave uncovered to firm up for at least an hour or overnight.
To make the ears, roll out the remaining black fondant icing to about 2mm thick. Cut out small leaf or teardrop shapes with a knife or a leaf shape cutter. You will need 24 in total. Repeat with the green fondant, cutting the leaf shapes slightly smaller than the black ones.
Take one of your black ears and lay one of the green pieces on top in the centre of the black piece and slightly down from the top. Carefully pinch the bottom of the ear together to make a shape that resembles a unicorn ear. Trim off the bottom of the ear so it forms a straight line then place on a piece of greaseproof paper. Repeat 24 times so you have 12 sets of ears then leave to firm up, uncovered for at least an hour or overnight.
Preheat oven to 180°C/160°C/Gas Mark 4 and take a 12 hole muffin tray or deep-hole bun tray and line with 6 green and 6 orange paper muffin cases.
Put the butter and sugar in a mixing bowl and beat with a wooden spoon or electric mixer until pale in colour and fluffy in texture. In a jug beat together the eggs, vanilla then add to the butter and sugar mixture along with the flour, baking powder and cocoa powder. Beat the ingredients together until smooth
Spoon the mixture into the paper cases filling about two-thirds full. Bake for 20 minutes or until firm to the touch or an inserted skewer comes out clean. • Remove the tray from the oven and allow to cool for 10 mins before transferring the cupcakes to a wire rack to cool completely.
Whilst the cupcakes are cooling make your buttercream. Put the room temperature butter in a large bowl and beat until light and fluffy with either a wooden spoon, handheld electric mixer or freestanding mixer. Add the icing sugar, milk and vanilla then beat again for a few minutes until light and fluffy in texture.
Divide the buttercream evenly between 3 bowls then mix in each colour, one per bowl, mixing well until the colour is evenly distributed. Put each coloured buttercream into a piping bag then lay out a large piece of cling film and pipe 3 thick, long lines of each buttercream next to each other onto the cling film, repeat until you have 6 lines of buttercream – 2 of each colour.
Roll up the buttercream in the cling film to make a long sausage. Cut off the end of the cling film then place the sausage of buttercream into a large piping bag fitted with an open star nozzle. (see our website for a tutorial on how to do rainbow swirl buttercream)
Pipe a swirl of the rainbow buttercream on top of each cupcake then top with two ears and a unicorn horn.