1. Heat the oven to 180C/160C fan/gas 4. Grease and line three 20cm round cake tins. In a large bowl, beat the butter and sugar until light in colour and fluffy in texture.
2. In a jug, beat together the eggs, Dr. Oetker Madagascan Vanilla Bean Paste and milk, then add to the butter mixture along with the flour and Dr. Oetker Baking Powder. Mix together until well combined.
3. Divide the mixture between the prepared cake tins, then bake for 30-35 mins, until a skewer inserted into the centre of each cake comes out clean. Allow the cakes to cool in their tins on a wire rack for 15 mins, then remove from the tins and allow to cool completely.
4. Once cool, place one cake on a plate. Using half of the Dr. Oetker Vanilla Buttercream Style Icing, spread a little onto the first layer of the cake, then add the second cake, spread another thin layer, then add the third cake and repeat. Crumb-coat the whole cake with the rest of the buttercream, thinly spreading it all over the top, then down the sides. Smooth it over with a palette knife.
5. Using the other half of the buttercream, spoon 100g into a piping bag and add the other 300g to a bowl. Stir in a handful of the Dr. Oetker Unicorn Confetti Sprinkles to create the funfetti buttercream, then cover the cake with it, smoothing the sides and top with a palette knife.
6. Add the marshmallows, golden syrup and butter to a heatproof bowl and place over a pan of barely simmering water to melt. Stir until everything has melted and combined to form a smooth paste. Add a couple of drops of the pink Dr. Oetker Extra Strong Food Colour Gel, then stir. Spoon the marshmallow mixture into a piping bag, then snip off the end to create a ½cm-wide hole. Allow to cool for about 5 mins until warm to the touch. Pipe around the edge of the cake in 1cm blobs and allow to slowly drip down the sides of the cake. Once there are drips all around the sides of the cake, use the rest of the marshmallow mixture to cover the top.
7. Snip off the end of the piping bag containing the reserved buttercream to make a 2cm hole. Pipe buttercream kisses around the edge of the top of the cake by holding the piping bag upright and squeezing to create a round 3cm shape, then pulling away to make a nice peak.
8. To finish the cake, sprinkle the top with some more Dr. Oetker Unicorn Confetti.