Preheat the oven to 200oc/180oc fan and grease and line three 18cm round tins.
In a large bowl or stand mixer, add the lemon juice to the almond milk and leave to stand for a few minutes to thicken. Add the sugar, oil and vanilla and whisk together until well incorporated.
Sift together the flour, cornstarch and bicarbonate of soda then add a little at a time to the wet mix, mixing well before adding more. One combined to a pourable batter, add the sprinkles then divide between the prepared cake tins. Sprinkle over a little extra sprinkles on top for extra colour.
Bake the cakes for 25 to 30 minutes until golden brown and a skewer inserted in the middle comes out clean.
Once baked, leave the cakes to cool in their tins for 10 minutes then carefully remove and cool completely on a wire rack. The cakes are very fragile so be quite careful.
For the cake crumbs, keep the oven at 200oc/180oc fan and mix together the dry ingredients in a bowl using a fork. Add the vanilla and oil and whisk together, until the mix clumps together. Pour onto a tray lined with baking parchment, taking care that there are some larger cake crumbs and some smaller ones before baking for 20 minutes, turning halfway through. Once golden, remove from the oven and leave to cool completely.
To prepare the cake soak, whisk together the almond milk and vanilla paste then set to one side.
For the frosting, place the vegan butter and vanilla into a large bowl or a stand mixer and beat for around 5 minutes until the butter is smooth and light in colour. Add half the icing sugar and beat again until pale and fluffy. Repeat with the remaining icing sugar until you have a thick buttercream frosting. Place into a large piping bag and snip off the end.
To assemble, dollop a little buttercream on a board or serving plate then place the first cake on top to secure it. Brush over some of the cake soak over the top of the cake then pipe a thick circle around the edge of the cake. Fill the circle with buttercream then smooth. Sprinkle over a handful of the cake crumbs then carefully place the second cake on top and repeat. Place the third cake on top and again pipe a circle around the edge then fill with buttercream.
To give the cake its signature ‘naked’ look, pipe buttercream into any holes that emerge between the cake layers. Don't worry if it looks messy, some of the frosting will be scraped away. Using a tall cake scraper held perpendicular to the cake, smooth the edges as you turn the cake away from you, stopping to scrape off any excess buttercream. Once the cake looks more uniform in shape, top the cake with any extra buttercream the decorate with the remaining cake crumbs and extra sprinkles. Keep the cake refrigerated until you’re ready to serve.
Recipe by Victoria Sponge Pease Pudding at http://victoriaspongepeasepudding.com/baking/vegan-milk-bar-birthday-cake/