1. Bake THREE 15cm round cakes using this vanilla sponge cake recipe. Bake your cakes at least one day prior to decorating.
2. Make the white chocolate ganache as follows and set it aside to firm up. Place a medium-size stainless steel bowl over a saucepan of simmering water. Add the chocolate and cream to the bowl, and stir continuously with a wooden spoon until the chocolate has just melted and is combined with the cream to a nice glossy finish. Remove the bowl from the heat and allow to cool.
Ganache can be made in advance. Covered in the fridge, it will keep for up to 2 weeks. Before using, bring it back to room temperature then mix well. It should be the consistency of toothpaste – not runny, not solid and just a little sticky. If it is too hard to stir, warm it slightly by giving it short 10-second bursts in the microwave or, alternatively, in a heatproof bowl over a saucepan of simmering water. If it is too runny, leave it to cool in the fridge.
3. Make the sugar syrup
Combine sugar and water in a small saucepan and bring to a simmer over a medium heat, stirring constantly until the sugar is dissolved. Simmer the syrup for 3–5 minutes or until the sugar has dissolved. Remove from the heat and leave to cool.
4. To make the sugared roses: Remove the leaves and thorns from the rose stems and discard them. Tip caster sugar onto a plate. Using a pastry brush, lightly paint the petals with the cooled sugar syrup, completing one rose at a time, and then sprinkle them with caster sugar. Place the flowers in a vase to dry (the stems can still be in water to keep the roses fresh).
5. Level the cakes using a cake leveler if possible. Turn cakes over.
6. Take the first cake for the stack and evenly spread ganache over the top surface, then place the next layer on top. Repeat.
7. Crumb coat the stacked cake by applying a thin layer of ganache with a palette knife or offset spatula to achieve a very thin, smooth finish (you should be able to see the cake through the icing). Never wipe excess crumb-coat icing back into the main bowl of icing as it will be full of crumbs and spoil the rest of the icing.
8. Refrigerate cake until dry to the touch.
9. Place the cake on a serving plate and completely cover it in ganache. Use a palette knife to create a textured look.
10. Push the flower picks into the top of the cake, making sure that they’re evenly spaced. Shortly before serving the cake, trim the rose stems to your desired length and insert them into the flower picks.
The purpose of the flower picks is to prevent the flower stems from seeping sap into the cake. They are available from specialty cake stores, but if you cannot source them you can use wider smoothie straws as a substitute. Just make sure you wrap the ends of the stems with plastic wrap before inserting them into the straws.
Sugared roses will continue to open, so choose flowers that are semi-closed and will last well without water once they’re inserted into the cake.
You can use lightly beaten egg whites instead of sugar syrup if you wish.