1. Grease both cake tins with oil, then line the base and sides with parchment paper.

2. Melt the butter for the cake in a large saucepan over a medium heat. Add the marshmallows and stir with a heatproof rubber spatula until melted. Tip in the Rice Krispies and 75g of the edible pearls and stir gently until well coated.

3. Working quickly before it sets, spoon the mixture into the two tins, pressing it down gently with the back of your spoon to compact it as you go. Fill them right to the top, levelling the mixture flat. Cover both with cling film and leave for 1 hour to cool and set firm – or until ready to use; they can be prepared up to 24 hours in advance.

4. Meanwhile, make the buttercream, which is easiest with an electric food mixer. Beat the softened butter in a large bowl until pale. Sift in the icing sugar and beat well to give a smooth mixture. Add the vanilla extract and milk and blend to loosen a little. Add the blue colouring a tiny bit at a time until you reach your preferred shade. The colour will intensify as the icing sits, particularly when out of the fridge. Cover and refrigerate for about 15 minutes to firm up a little. This can be prepared up to 24 hours in advance and left in the fridge, but it will harden, so remove it about 15 minutes before you need it to let it soften up.

5. When the cakes are set, carefully lift from the tins and remove the paper. Spread a couple of tablespoons of buttercream in the centre of a stand and stick down the larger cake. Then spread another tablespoon of icing in the middle of the cake and stick the smaller cake well centred on top.

6. Spoon the remaining icing into the piping bag. Starting at the bottom of the larger cake, hold the piping bag vertical against the side of the cake with the wide end of the petal nozzle touching the cake and the thin end pointing outwards. Now pipe back and forth across a 1.5-2cm width, working upwards until you reach the top of this cake and firmly squeezing the bag as you go. That’s one frill done, now repeat until the sides of both cakes are covered.

7.To ice the tops of the cakes, start from the outside and work inwards, with the bag held vertical and the fat end of the petal shape facing the centre, this time working the back and forth motion around the outer edge. Then pipe another circle inside and so on, until the tops are completely covered.

8.Finally, sprinkle with the remaining edible pearls and go wow your guests. The easiest way to cut this is to lift the top cake carefully onto a chopping board. Then cut into 8 wedges and the larger cake into 12 wedges, and serve.

Photo © Marc Dillon