Take a bowl and put a sieve on it.
Add flour, cocoa powder, cornflour, baking powder, baking soda, coffee powder and salt.
Sift the dry ingredients into the bowl.
Add brown sugar and refined sugar.
Give them a good mix.
Create a vacuum in the middle.
Add oil, vanilla essence and vinegar.
Now start adding mixing while adding hot water.
Keep whisking simultaneously.
Mix. Make sure there remains no lumps.
Transfer this batter in a cake tin lined with greased butter paper.
Tap the tin few times so that there remains no air bubbles.
Bake in a preheated oven @180°C for 40-45 minutes.
Check by inserting a toothpick and if it's come out clean, its a sign that cake is thoroughly baked.
Place the cake tin on wire rack and let it cool down a bit for 15-20 minutes only. Don't wait to let it cool down completely.
Invert the cake.
Now let the cake cool down completely. If you like, you can stop the process here and start enjoying the cake. But we will go ahead to make it super chocolaty.