Step 1

Prepare: Preheat your oven to 175°C (347°F). Lighty grease the base and sides of three 6" cake tins with oil. Line each base with a circle of parchment and the sides with a strip of parchment.To make the vegan buttermilk add the soy milk and apple cider vinegar to a mixing jug, stir and allow to sit for 10 minutes.

Step 2

Blend the nuts and sugar: Add the pistachios and sugar to a food processor or blender, and blitz until finely ground.

Step 3

Mix the dry ingredients: Add the pistachio sugar mixture, flour, baking powder, and salt to a large mixing bowl and whisk to combine.

Step 4

Mix the wet ingredients: Add the olive oil, vanilla extract, and almond extract to the jug with the vegan buttermilk and whisk to combine.

Step 5

Make the batter: Pour the wet ingredients into the bowl with the dry ingredients and use a spatula to carefully fold and mix the ingredients. Stop folding once there are no visible pockets of flour - don't be tempted to overmix!

Step 6

Bake: Transfer the cake batter to the lined cake pans and bake in the preheated oven for 20-25 minutes. To check they are done, insert a skewer or toothpick into the center, it should come out almost clean with a few crumbs, but without any wet batter.

Step 7

Cool the cakes: Allow the cakes to cool in the tins for 15-20 minutes and then carefully turn them out onto a cooling rack to cool further for at least an hour until cool to the touch. Carefully peel away the parchment that will stick to the base of the cakes.If preferred you can refrigerate the cakes in an airtight container until ready to use. Chilling the cakes for a few hours (or overnight) makes them easier to work with and decorate.

Step 8

Make a half batch of pistachio buttercream (or a full batch and freeze half for another time).Add the frosting to a piping bag fitted with a round nozzle, or simply snip off the end of a ziplock bag/piping bag when ready to decorate.

Step 9

Assembly: Place a tiny amount of frosting on a cake turntable and secure the first sponge layer on top of it.Pipe a layer of frosting on top of the first cake layer, and use an offset spatula/pallet knife to spread it in an even layer.Add the next layer of cake and repeat with another layer of frosting. Top with the final layer of cake. Use the remaining frosting to coat around the sides on top of the cake and smooth everything out with a cake scraper.

Step 10

Storage: Store in an airtight container in the fridge for up to 5 days or at room temperature for up to 1-2 days. Remove from the fridge about an hour before serving to allow the cake and frosting to soften a little.