Grease the cake pan and set aside.
In a small bowl mix the instant coffee powder with the warm milk and set aside.
In a large bowl whisk together the sugar and butter till the sugar dissolves completely. Add the coffee mixture, vanilla essence and eggs one at a time and beat nicely until all is combined.
Now add the melted chocolate and whisk nicely, followed by the dry ingredients and mix everything together gently to make a smooth batter.
Now pour the batter into the greased pan and microwave on high for 6 mins. Since the standard temperature of the microwave varies from one another start checking from 5 mins onwards. A tooth pick inserted should come out clean.
Take out from microwave and let it cool. Demould it, cut and serve.