Decadent chocolate cake

Instructions

1. To make the custard, in a bowl, whisk together the sugar, egg yolks, cornflour and salt. Place a saucepan over low heat, add sour cream, thickened cream and vanilla pod, whisking constantly. Once the mixture boils, whisk one cup of the cream mixture into the yolk mixture. Remove the vanilla bean, then whisk the remaining yolk mixture with the cream mixture. Transfer to a bain-marie over simmering water and cook, whisking constantly until it thickens. Remove from heat, place cling film directly on top of the surface of the warm custard and seal the bowl so it doesn’t form a skin on top. Refrigerate overnight.
   
2. To make the diplomat cream, in a large bowl, whip 500 g thickened cream, 1 ¾ cups sifted icing sugar and 3 tsp vanilla extract until firm peaks form. Gently fold the whipped sweetened cream into the chilled custard. Keep refrigerated at all times.
   
3. Preheat the oven to 180˚C (or 160˚C fan-forced). Spray 2 x 20 cm round cake tins with canola oil spray, then line the tins with baking paper.
   
4. To make the cake batter, in the bowl of a stand mixer with the paddle attachment fitted, combine the flour, sugar, cocoa powder, bicarb soda, baking powder and salt. Mix on low speed to combine. With the motor running, add the eggs, sour cream and vegetable oil.
   
5. Combine the boiling water and coffee in a jug, whisking well to dissolve. Gradually add this to the cake batter mixture, mixing on low speed, to form a thick batter. Occasionally pause and scrape the bottom and sides of the bowl with a flexible spatula.
   
6. Weigh out 400 g cake batter to fill each prepared tin and smooth the tops with an offset spatula. Bake for 22 minutes, or until a skewer inserted into the centre comes out dry.
   
7. Remove the cakes from the oven and trim the domed tops, using a serrated knife, so the cakes have a flat, smooth top (reserve the domed tops for later!) Cut the cakes in half horizontally – you will need three cake layers for this recipe. You can freeze the remaining cake layer and keep it for another use.
   
8. Place one layer of cake on your serving plate and brush generously with 1/3 cup water (this will add moisture, without the sickly sweetness of sugar syrup). Spread over a layer of dulce de leche (see Note), followed by 1 ½ cups diplomat cream (see Note), spreading evenly over the cake. Push 12-14 raspberries into the cream and smooth out evenly with an offset spatula. Add a second layer of cake and repeat the process with the caramel, diplomat cream and raspberries, finishing with a third layer of cake. Brush with an extra ¼ cup water, then refrigerate for a few hours, or overnight.
   
9. Place the domed tops of the cake into a food processor and process to very fine crumbs, then transfer to a medium bowl, cover and set aside until required.
   
10. To finish the cake, spread diplomat cream over the sides and top of the cake. Use a piping bag fitted with a star nozzle to pipe extra diplomat cream swirls around the top of the cake. Decorate with the processed cake crumbs and remaining raspberries to finish.

• Dulce de leche is much easier to use when slightly warmed before spreading between the cake layers.
  
• Diplomat cream is made by combining sweetened vanilla whipped cream (also called Chantilly cream) with custard.