1) For the chocolate cake: Mix granulated sugar, sour cream, whole milk, instant espresso, vegetable oil, whole eggs and vanilla essence in a standing mixer on low speed for approximately 2 minutes or until combined. Scrape the bowl and add the flour, cocoa powder, bicarbonate of soda, baking powder and kosher salt. Mix another 2 to 3 minutes until cake batter is smooth. Pour into sprayed and parchment lined 25-cm cake pan. Bake for 20 minutes or until toothpick inserted in the center of the cake comes out clean. Set aside to cool.
2)For the chocolate mousse:
Melt chocolate and set aside (keep warm). In a separate dish add powdered gelatine to cold water, set aside. Whisk together milk and egg yolks in a saucepan. Put on a medium flame and cook until 74 degrees C. Be careful not to over cook and curdle the mixture. Pour egg-milk mixture through a strainer into the melted chocolate. Melt the gelatine and water. Add to the chocolate mixture and stir until combined. Let chocolate mixture cool to room temperature. Whip the double cream to soft peaks and fold into the chocolate mixture.
3) For the ganache: In a saucepot combine double cream, sugar and unsalted butter. Bring to a boil. Take off flame. Add chopped chocolate to boiled cream let sit for 1 minute then stir until combined. Over-mixing will cause bubbles in the ganache. Only stir until chocolate is incorporated. Set aside.
4) For the chocolate buttercream: In a saucepan combine granulated sugar and just enough water to moisten the sugar. Bring to a boil, washing down the sides as you go with a brush dipped in water. Bring to 115 degrees C. As sugar is cooking, begin whipping the egg whites in a mixer on medium speed. Increase speed, as sugar gets closer to a soft peak. Mix the unsalted butter, vegetable fat and salt together. When sugar reaches temperature pour into whipping egg whites. Continue to whip on high speed until the mixing bowl is just warm to the touch. Quickly add the unsalted butter, vegetable fat and salt. Continue to whip for 5 minutes or until buttercream comes together and is smooth. Add melted chocolate and cocoa powder. Whip until combined. Set aside.
For Assembly: Slice 25-cm cake horizontally into 2 even pieces. Place first layer of cake in a cling film lined 25-cm cake pan. Spread a thin layer of raspberry marmalade on top of the cake. Spread a thin layer of chocolate ganache on the raspberry marmalade. Spread a 6-cm thick layer of chocolate mousse on top of the ganache. Top with the second layer of chocolate cake and refrigerate for 1 hour. Remove the cake from the refrigerator and spread a layer of chocolate butter cream on top of the cake. Spread a layer of chocolate ganache on top. Put the cake in the freezer for 1 hour or longer. Remove from the freezer and gently pull cake out of the pan by pulling on the plastic wrap. Keep refrigerated until served.