As we are already adding the cocoa and coffee, the cake will be dark. But if you want it darker, you can add some caramel too. As mentioned above, there are two ways to caramelise sugar. One is a time consuming method whereas the other takes less time, but one needs to be extra cautious.
Easy method:- Heat sugar in a pan till it turns dark brown in colour. Away from heat, carefully add water, a little at a time, into the caramel. It is better one keeps a safe distance, as the contents may splash.
Time consuming method:- Take sugar and water with few drops of lime juice. Heat till it turns dark brown in colour. Set aside to cool.
Once cool, add the brandy/rum and mix well. Now add the dried fruits, except the nuts, and mix well. This can be prepared and stored in an airtight container for a long time. Make sure to shake the container once in a while.
Preheat the oven at 180C.
Sieve the flour along with baking powder, cardamom powder, clove powder and cinnamon powder a few times. Keep aside.
Add the chopped nuts to the soaked fruits. Sprinkle 2-3 tablespoons of the extra flour onto the dried fruits and mix well. This is to ensure that the dried fruits don't sink to the bottom of the pan.
Cream the butter and sugar together till pale in colour. Add one egg at a time, and mix well. Gradually fold in the flour mixture.
Add the fruit mix, cocoa decoction as well as the coffee decoction and mix well (if using more caramel, you can add it now). Pour the cake mixture into a greased baking tin.
Bake in the preheated oven for 30-40 minutes, till the cake is cooked through. Insert a toothpick into the centre of the cake. The cake is cooked if it comes clean. Remove the cake from the oven and allow to cool completely before slicing the cake.