This is just for fun not for eating.
Prepare Mysore Mallige Idli Batter. Put some batter in a small glass coated with oil (any oil sunflower oil, sesame oil, coconut oil etc). Steam it till batter gets hardened. Dissolve 2 teaspoons of instant coffee in 2 tea spoons of water. Take two cups with idli batter and add this coffee mix to these cups to get a dark shade and light shade. (mix a small quantity of coffee for one cup and a large quantity of coffee in another. Pour dark mix on hardened idli in glass. Steam again . Garnish with light coloured batter. I have named it as dalgona idli