Preheat the oven at 100 degree C.
Melt the butter in a double boiler. Keep it aside and let it cool completely.
In a mixing bowl, whisk the butter. Add the sugar, a teaspoon at a time, and continue whisking until well combined.
Add the eggs and whisk well.
Sift together the ragi flour and baking powder. Add it, a teaspoon at a time to the above mixture while you continue folding. Ensure that no lumps are left behind but do not over mix.
Dissolve the instant coffee in 4 Tbsp hot water and pour it into the above mixture.Give it a final fold, and transfer to a small baking tin (6 inch diameter). Bake in the oven at 150 degree C for 15 minutes or until a skewer inserted at the center of the tin comes out clean.
For the Kahlua Chocolate Ganache
Pour the cream in a saucepan and place it on a medium flame. Continue stirring until it comes to a slight boil.
Chop the chocolate into smaller chunks and place them in a mixing bowl. Pour the hot cream over it and let it stand for 7-8 minutes.
Whisk the mixture until smooth and creamy. Add the Kahlua and whisk again. Let it cool completely at room temperature before applying it on the cake.
Note: You can also sprinkle some cocoa powder on top before serving.