For the peanut butter frosting:

300g (around 1&3/4 cups) dark chocolate (I used 54% cocoa solids but 70% would be even better)

90g (1/2 cup) white chocolate (for the shards)



Method:





1. Preheat the oven to 180c (160c fan)/355f/gas mark 4. Grease the base and sides of a loose-bottomed (or springform) 15cm and a 23cm round cake tin. Dust with a little flour.





2. To make the cake, pour the margarine and sugar into the bowl of a stand mixer, with the paddle attached. Start the mixer on a low speed and cream the margarine and sugar together until it is light and fluffy.





3. Sift the flour and cocoa powder into a mixing bowl.





4. Add the eggs, one at a time, to the butter/sugar mixture, adding a tablespoon of the flour/cocoa powder after each egg.





5. Add the remaining flour/cocoa, and the yoghurt, salt and coffee. Turn the stand mixer to a low setting, and mix together just until all of the flour has been incorporated.





6. Divide between the two tins so that they are about 2/3 full each. Bake. The 23cm tin will take about 35-40 minutes to cook, the 15cm should take 55-60 minutes. They are cooked when a skewer inserted into the centre of the cake comes out clean, and the cakes are springy to the touch.





7. Leave to cool for a few minutes, before turning the cakes out of the tin onto wire racks to cool fully.





8. Make the frosting by heating the water with the sugar in a small saucepan, stirring occasionally until the sugar has dissolved.





9. Pour the eggs and egg yolk into the bowl of a stand mixer fitted with the whisk attachment, and start whisking on a medium speed until they have at least tripled in volume and become light in colour.





10. Keep heating the sugar and water until a sugar thermometer dipped in the syrup reads 113c/235f. As soon as it reaches this temperature, turn off the heat and VERY CAREFULLY, pour the syrup over the egg yolks, making sure the speed of the mixer is set to low. Once all of the syrup has been added, turn up the speed of the mixer (to about medium) and keep whisking until the side of the bowl no longer feels warm (about 10 minutes). The mixture will get very light, but not hold as firm peaks as the traditional meringue would.





11. Once cooled to room temperature, keep whisking whilst adding the butter, a cube at a time. Don't add too much butter at once, or the buttercream may split.





12. Once all of the butter has been added, add the peanut butter and cinnamon, mix and taste. If needed add a little salt or more peanut butter. Place in the fridge until ready to use.





13. To assemble the cakes, use a serrated knife to level off the top of each cake, then slice each cake into two.





14. Place the first 23cm cake onto your serving dish. Add 2-3 tbsp of the frosting and smooth over the top of the layer. Gently press on the second 23cm cake layer, and then cover the top and sides of the cake with more frosting. There should be more than enough frosting to cover and fill these cakes, so you shouldn't have to worry about running out.





15. Place the first 15cm cake layer onto the centre of the 23cm cake. Top with 2 tbsp of the frosting, and add the final layer of cake. Cover with more peanut butter frosting, and then chill for 20 minutes.





16. It's chocolate collar time! Prepare your acetate sheets - they need to be a little taller than your 15cm cake, and around 51cm wide (which should be the circumference of the cake, you can check this if you like). Once prepared, place on a surface you don't mind getting covered in chocolate...





17. This is how I temper chocolate. Break two-thirds of the chocolate into cubes and put in a microwave-safe bowl. Heat for 20-30 second bursts, stirring well after each burst. During the bursts, finely chop the remaining third of the chocolate.





18. Once all of the chocolate has melted, remove from the microwave and pour in the remaining chopped chocolate. Stir until the chopped chocolate has melted and then pour onto a granite slab.





19. Use a palette knife to spread the chocolate around the slab, scooping it up into a line, then spreading out and repeating. You'll notice the chocolate starts to get thicker. At this point, spoon the chocolate back into a bowl and QUICKLY spread out evenly over the acetate mould, going over the edges.





20. Wait for a few minutes, until the chocolate looks light it is starting to set - this is difficult to judge but it shouldn't take more than 3 minutes. Gently press the collar around the cake, leaving the acetate facing outwards for now. Leave for another few minutes, and then, when you think the chocolate has fully set, gently pry away the acetate.





21. I tempered more white and dark chocolate and spread them on some spare plastic wallets I had. Once cool I broke these into shards to decorate the top and sides of the cake. Next time I might try some different chocolate decorations - if you do anything cool, please let me know!





22. Enjoy!







