Filter coffee is a flavour that does not translate well from coffee extract or instant. We had to start with real decoction.
We brew fresh decoction the morning of baking using Kumbakonam degree coffee powder from a Mylapore supplier. The decoction is intense — much more concentrated than a cup of coffee you would drink.
In the sponge, we replace the milk with a 1:1 mix of decoction and milk. The colour deepens and the cake takes on a clear coffee aroma.
In the buttercream, we whip the decoction with the butter and use unrefined cane sugar instead of icing sugar. The cane sugar gives a slight caramel note that balances the bitterness of the coffee. White icing sugar would just be sweet, missing the depth.
Finish: thin dust of cocoa powder, or simple plain finish. We avoid heavy fondant on this cake because the flavour pairs better with a buttercream texture.
Who orders. Most reorders come from customers above 40 who grew up with morning filter coffee. They tell us it tastes like the kitchen they grew up in.
Not suitable for kids under 8 (caffeine, and the bitterness is unfamiliar). Good for office birthdays — most South Indian colleagues will recognise and enjoy.
Eggless variant: works well, slightly more dense sponge.