Beat your softened butter and vanilla extract until pale and fluffy.
Gradually add your icing sugar, using a spatula work it into your beaten butter or cover the bowl with a clean tea towel to stop it billowing up. Then beat it in with your hand or stand mixer.
Place the tier you are going to use as your base tier on your lazy Susan (or turntable).
Split your butter cream into 4 equal parts.
Take one portion of your butter cream and spread half of it over the Malteser cake base as a filling. Place the other tier on top then cover the whole cake with the rest of the butter cream. Use your palette knife or butter knife to even the butter cream out and then use your cake scraper to level the sides.
Place your cake in your refrigerator to set for 20 minutes.
Mix your Horlicks with your milk until all the lumps have gone. Mix into one of your remaining lots of butter cream.
Melt your chocolate (you can do this in short 10 second bursts in your microwave). Mix the chocolate into another of your lots of butter cream.
You will now have one Horlicks butter cream, one chocolate and one vanilla.
Taking your palette knife spread some of your chocolate butter cream over the lower half of the side of your Malteser cake.
Spread some of your Horlicks butter cream over the top side of the cake, making sure it meets or slightly overlaps the chocolate butter cream.
Cover the top of the cake with some chocolate butter cream.
Take your cake scraper and run it around the cake to great a smooth surface.
Take your Wilton fill 3 colour swirl piping bags and pipe swirls around the edge of the cake.
Pipe stars around the the base.
Fill the centre of the cake with Maltesers.