- 2 eggs, whites only
- 425g caster sugar, or granulated sugar
- 100 ml water
- Bring to the boil a saucepan of water large enough to hold a heatproof bowl. Place the egg whites in the bowl and whisk with a hand-held electric beater until very stiff.
- In a separate saucepan over a medium–high heat, dissolve the sugar in the water and boil for 5–10 minutes until the liquid is thick and syrupy and has reached the 'thread' stage – when the last few drops that fall from a metal spoon dipped into the syrup come off in one long, quite thick and syrupy thread
- Pour the boiling syrup over the stiffly beaten egg whites, whisking all the time with the hand-held beater. Place the bowl in the saucepan of simmering water. Continue to whisk over the water for 10–15 minutes until the icing is snow white, very thick and meringue-like.
- Spread quickly over the cake with a palette knife, regularly dipping the knife into a jug of boiling water to help spread the icing. It sets very quickly at this stage, so speed is essential.
- Scatter with rose petals, if using, or arrange the walnut halves around the top of the cake, and allow the icing to set until it feels dry on the surface.