For the pistachio layers:
- 90g unsalted butter
- 110g caster sugar
- 100g plain flour
- 1 tsp baking powder
- 2 eggs
- 20g ground pistachios
For the rose buttercream:
- 75g egg white (2-3 eggs worth)
- 110g granulated sugar
- 125g unsalted butter, at room temperature
- 2 tsp rose water
To assemble & decorate :
- 1 unsprayed rose
- 1 egg white
- 50g caster sugar
- 20g ground pistachios
- Preheat the oven to 170C. Grease two 5″ round tins. Beat the butter and sugar until pale and fluffy. Sift the flour and baking powder into the bowl and add the eggs and pistachios. Beat to combine. Divide between the two tins. Bake for 20-25 minutes until a skewer can be removed cleanly from the centre. Cool in the tins for 5 minutes then remove to a wire rack until cool.
- To make the sugared petals, carefully pull the petals off the rose. Discard any bruised or brown petals. Separate an egg and put in a small pot. Put the sugar in a small bowl/pot. Using a paintbrush or pastry brush, lightly cover a rose petal in the egg white. Either carefully press the petal into the sugar or sprinkle it on. Put to dry on a sheet. Repeat for all your petals. Leave to dry for about 30 minutes or until fairly hard before using.
- For butter-cream – When you’re ready and have all your ingredients set out, combine the whites and sugar in a medium heatproof bowl and place it over a pan of simmering water. Whisk until the temperature hits 160F and the mixture is smooth (check by rubbing a little between your fingers).
- Transfer to a stand mixer (or just use a hand whisk with the same bowl) and start whipping on medium-high. Whip for about 8 minutes – it should be really thick and glossy and gorgeous. Check that it is room temperature – if not leave it for another minute or two slowly whisking. Turn the speed back up to medium/high and add a piece of butter (should be about tbsp sized pieces). Whisk until totally incorporated, then add another. Repeat until all the butter is used.
- At this point if it looks soupy and thin, pop it in the fridge. If not, keep whipping until it is thick and luxurious again – this can take quite a while. When ready, whip in the rose water teaspoon by teaspoon, checking after each addition for taste.
- Split each of the cakes into two. Place four strips of greaseproof paper on your cake plate and then place one of the layers on top. Remove 1/3 of the butter cream to another bowl and fold in the pistachios. Spread a 1/3 of this pistachio buttercream over a layer. Repeat with the rest of the layers.
- Use some of the remaining plain rose buttercream to smooth a thin layer of icing over the cake – a crumb coat. Place in the fridge for 10 minutes. Finally use the remaining butter cream to put a final coat of icing on top of the crumb coat. Arrange the rose petals on top of the cake and sprinkle with a few remaining pistachio crumbs if desired.