Divide the batter into 2 bowls. Add the spinach puree to one bowl and mix well. Grease the idli moulds.
Pour some of the white batter first. Then pour the spinach batter over it and continue to do so, alternately pouring the batter.
Steam in a pressure cooker (without the vent) or steamer for 15 minutes (first 5 minutes on high and the remaining on a medium flame).
Demould the idlis when it slightly cools down and serve with coconut chutney and sambar.
