Make the Cake Batter

1. Preheat your oven to 160°C fan.Dissolve the instant coffee granules in the hot water and set the mixture aside to cool.
2. In a large mixing bowl, combine the vegetable oil, caster sugar, and light brown sugar. Whisk until well blended.
3. Add the eggs, one at a time, whisking well after each addition until fully incorporated.
4. Pour in the vanilla extract and the cooled coffee mixture, then give everything a quick whisk.
5. Add the sour cream and whisk until smooth and well combined.
6. Place a sieve over the bowl and sift in the plain flour, cocoa powder, baking powder, baking soda, and salt.
7. Using a spatula, gently fold the dry ingredients into the wet ingredients until no dry flour remains. The batter may look a little lumpy at this stage, but don’t worry—that’s perfectly normal. Switch back to the whisk and whisk until the batter is smooth and cohesive.
8. Generously spray a 12-cup Bundt pan with cake release spray, making sure to coat all the grooves and decorative details. This will help the cake release beautifully after baking.
9. Pour the batter into the prepared Bundt pan.  Gently smooth the top if needed.
10. Bake in the preheated oven at 160°C fan for 50 minutes, or until a skewer inserted into the centre comes out clean.
11. Once baked, remove the cake from the oven and let it rest in the pan on a wire rack for about 15 minutes.
12. When the pan is cool enough to handle, place a wire rack over the top and carefully invert the pan to release the cake. It should come out easily. Leave the cake on the wire rack to cool completely before decorating.

Make the Chocolate Ganache

1. Chop the chocolate into small pieces and place them in a heatproof bowl.
2. Heat 150 ml double cream in the microwave for 1–2 minutes, or until warm but not boiling.
3. Pour the warm cream over the chopped chocolate. Cover the bowl and let it sit for 5 minutes.
4. Remove the cover and stir until the chocolate and cream are smooth and well combined.
5. Add the remaining double cream and stir until fully incorporated.
6. Cover the surface of the ganache with cling film to prevent a skin from forming.
7. Refrigerate until needed.

Decorate the Cake

1. Make sure the cake is completely cool before decorating.
2. Spread a generous amount of ganache over the surface of the cake.
3. Fill the centre of the bundt cake with assorted chocolates for a surprise filling, then cover the chocolates with ganache.
4. Add any decorations of your choice and enjoy!